Permutations/Derangements
You are encouraged to solve this task according to the task description, using any language you may know.
A derangement is a permutation of the order of distinct items in which no item appears in its original place.
For example, the only two derangements of the three items (0, 1, 2) are (1, 2, 0), and (2, 0, 1).
The number of derangements of n distinct items is known as the subfactorial of n, sometimes written as !n. There are various ways to calculate !n.
- Task
- Create a named function/method/subroutine/... to generate derangements of the integers 0..n-1, (or 1..n if you prefer).
- Generate and show all the derangements of 4 integers using the above routine.
- Create a function that calculates the subfactorial of n, !n.
- Print and show a table of the counted number of derangements of n vs. the calculated !n for n from 0..9 inclusive.
- Optional stretch goal
- Calculate !20
- Related tasks
- Metrics
- Counting
- Word frequency
- Letter frequency
- Jewels and stones
- I before E except after C
- Bioinformatics/base count
- Count occurrences of a substring
- Count how many vowels and consonants occur in a string
- Remove/replace
- XXXX redacted
- Conjugate a Latin verb
- Remove vowels from a string
- String interpolation (included)
- Strip block comments
- Strip comments from a string
- Strip a set of characters from a string
- Strip whitespace from a string -- top and tail
- Strip control codes and extended characters from a string
- Anagrams/Derangements/shuffling
- Word wheel
- ABC problem
- Sattolo cycle
- Knuth shuffle
- Ordered words
- Superpermutation minimisation
- Textonyms (using a phone text pad)
- Anagrams
- Anagrams/Deranged anagrams
- Permutations/Derangements
- Find/Search/Determine
- ABC words
- Odd words
- Word ladder
- Semordnilap
- Word search
- Wordiff (game)
- String matching
- Tea cup rim text
- Alternade words
- Changeable words
- State name puzzle
- String comparison
- Unique characters
- Unique characters in each string
- Extract file extension
- Levenshtein distance
- Palindrome detection
- Common list elements
- Longest common suffix
- Longest common prefix
- Compare a list of strings
- Longest common substring
- Find common directory path
- Words from neighbour ones
- Change e letters to i in words
- Non-continuous subsequences
- Longest common subsequence
- Longest palindromic substrings
- Longest increasing subsequence
- Words containing "the" substring
- Sum of the digits of n is substring of n
- Determine if a string is numeric
- Determine if a string is collapsible
- Determine if a string is squeezable
- Determine if a string has all unique characters
- Determine if a string has all the same characters
- Longest substrings without repeating characters
- Find words which contains all the vowels
- Find words which contains most consonants
- Find words which contains more than 3 vowels
- Find words which first and last three letters are equals
- Find words which odd letters are consonants and even letters are vowels or vice_versa
- Formatting
- Substring
- Rep-string
- Word wrap
- String case
- Align columns
- Literals/String
- Repeat a string
- Brace expansion
- Brace expansion using ranges
- Reverse a string
- Phrase reversals
- Comma quibbling
- Special characters
- String concatenation
- Substring/Top and tail
- Commatizing numbers
- Reverse words in a string
- Suffixation of decimal numbers
- Long literals, with continuations
- Numerical and alphabetical suffixes
- Abbreviations, easy
- Abbreviations, simple
- Abbreviations, automatic
- Song lyrics/poems/Mad Libs/phrases
- Mad Libs
- Magic 8-ball
- 99 Bottles of Beer
- The Name Game (a song)
- The Old lady swallowed a fly
- The Twelve Days of Christmas
- Tokenize
- Text between
- Tokenize a string
- Word break problem
- Tokenize a string with escaping
- Split a character string based on change of character
- Sequences
11l
<lang 11l>F derangements(n)
Int r V perm = Array(0 .< n) L I all(enumerate(perm).map((indx, p) -> indx != p)) r [+]= perm I !perm.next_permutation() L.break R r
F subfact(n) -> Int64
R I n < 2 {1 - n} E (subfact(n - 1) + subfact(n - 2)) * (n - 1)
V n = 4 print(‘Derangements of ’Array(0 .< n)) L(d) derangements(n)
print(‘ ’d)
print("\nTable of n vs counted vs calculated derangements") L(n) 10
print(‘#2 #<6 #.’.format(n, derangements(n).len, subfact(n)))
n = 20 print("\n!#. = #.".format(n, subfact(n)))</lang>
- Output:
Derangements of [0, 1, 2, 3] [1, 0, 3, 2] [1, 2, 3, 0] [1, 3, 0, 2] [2, 0, 3, 1] [2, 3, 0, 1] [2, 3, 1, 0] [3, 0, 1, 2] [3, 2, 0, 1] [3, 2, 1, 0] Table of n vs counted vs calculated derangements 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
360 Assembly
Due to 32 bit integers !12 is the limit. <lang 360asm>* Permutations/Derangements 01/04/2017 DERANGE CSECT
USING DERANGE,R13 base register
B 72(R15) skip savearea
DC 17F'0' savearea
STM R14,R12,12(R13) save previous context
ST R13,4(R15) link backward
ST R15,8(R13) link forward
LR R13,R15 set addressability
XPRNT PG1,L'PG1 print title
LA R1,4 4
LA R2,1 1 : combinations print
BAL R14,DERGEN call dergen
STH R0,COUNT count=dergen(4,1)
XPRNT PG2,L'PG2 print table headings
XPRNT PG3,L'PG3 print hyphens
SR R4,R4
STH R4,II ii=0
DO WHILE=(CH,R4,LE,=H'9') do ii=0 to 9
MVC PG,=CL80' ' clear buffer
XDECO R4,PG edit ii
LR R1,R4 ii
LA R2,0 0 : no combination print
BAL R14,DERGEN dergen(ii,0)
XDECO R0,PG+12 edit
LH R1,II ii
BAL R14,SUBFACT subfact(ii)
XDECO R0,PG+24 edit
XPRNT PG,L'PG print
LH R4,II ii
LA R4,1(R4) i+1
STH R4,II i=i+1
ENDDO , enddo i
LA R0,12 12
STH R0,II ii=12
MVC PG,=CL16'!xx=' init buffer
XDECO R0,XDEC edit ii
MVC PG+1(2),XDEC+10 output
LH R1,II ii
BAL R14,SUBFACT subfact(ii)
XDECO R0,PG+4 edit subfact(ii)
XPRNT PG,16 print
L R13,4(0,R13) restore previous savearea pointer
LM R14,R12,12(R13) restore previous context
XR R15,R15 rc=0
BR R14 exit
- ------- ---- -------------------------------------------
DERGEN EQU * dergen(n,fprt)
ST R14,SAVEDG
ST R1,N n
ST R2,FPRT fprt
IF LTR,R1,Z,R1 THEN if n=0 then
LA R0,1 1
B RETDG return(1)
ENDIF , endif
MVC C,=F'0' c=0
LA R6,1 i=1
DO WHILE=(C,R6,LE,N) do i=1 to 2
LR R1,R6 i
SLA R1,1
STH R6,A-2(R1) a(i)=i
STH R6,AO-2(R1) ao(i)=i
LA R6,1(R6) i++
ENDDO , enddo i
L R1,N n
BAL R14,FACT
ST R0,FACTNM1 fact(n)-1
SR R6,R6 i=0
DO WHILE=(C,R6,LE,FACTNM1) do i=0 to fact(n)-1
L R1,N n
BAL R14,NEXTPER call nextper(n)
MVI D,X'01' d=true
LA R7,1
DO WHILE=(C,R7,LE,N) do j=1 to n
LR R1,R7 j
SLA R1,1
LH R2,A-2(R1) a(j)
LH R3,AO-2(R1) ao(j)
IF CR,R2,EQ,R3 THEN if a(j)=ao(j) then
MVI D,X'00' d=false
ENDIF , endif
LA R7,1(R7) j++
ENDDO , enddo j
IF CLI,D,EQ,X'01' THEN if d then
L R2,C c
LA R2,1(R2) c+1
ST R2,C c=c+1
IF CLI,FPRT+3,EQ,X'01' THEN if fprt=1 then
MVC PG,=CL80' ' clear buffer
LA R10,PG pgi=0
LA R7,1 j=1
DO WHILE=(C,R7,LE,N) do j=1 to n
LR R1,R7 j
SLA R1,1
LH R2,A-2(R1) a(j)
XDECO R2,XDEC edit
MVC 0(1,R10),XDEC+11 output
LA R10,2(R10) pgi=pgi+2
LA R7,1(R7) j++
ENDDO , enddo j
XPRNT PG,L'PG print
ENDIF , endif
ENDIF , endif
LA R6,1(R6) i++
ENDDO , enddo i
L R0,C c
B RETDG return(c)
RETDG L R14,SAVEDG
BR R14
SAVEDG DS A
- ------- ---- -------------------------------------------
NEXTPER EQU * nextper(nk)
ST R14,SAVENP
ST R1,NK nk
BCTR R1,0 nk-1
ST R1,NELEM nelem=nk-1
IF C,R1,LT,=F'1' THEN if nelem<1 then
LA R0,0 return(0)
B RETNP
ENDIF , endif
L R8,NELEM nelem
BCTR R8,0 pos=nelem-1
LOOPW1 EQU * while a(pos+1)>=a(pos+2)
LR R1,R8 pos
SLA R1,1
LH R2,A(R1) a(pos+1)
CH R2,A+2(R1) if a(pos+1)<a(pos+2)
BL ELOOPW1 then exit while
BCTR R8,0 pos=pos-1
IF LTR,R8,M,R8 THEN if pos<0 then
LA R1,0 0
L R2,NELEM nelem
BAL R14,PERMREV call permrev(0,nelem)
LA R0,0 return(0)
B RETNP
ENDIF , endif
B LOOPW1 endwhile
ELOOPW1 L R9,NELEM last=nelem LOOPW2 EQU * do while a(last+1)<=a(pos+1)
LR R1,R9 last
SLA R1,1
LH R2,A(R1) a(last+1)
LR R1,R8 pos
SLA R1,1
CH R2,A(R1) if a(last+1)>a(pos+1)
BH ELOOPW2 then exit while
BCTR R9,0 last=last-1
B LOOPW2 endwhile
ELOOPW2 LR R1,R8 pos
SLA R1,1 *2
LA R2,A(R1) @a(pos+1)
LR R1,R9 last
SLA R1,1
LA R3,A(R1) @a(last+1)
LH R0,0(R2) w=a(pos+1)
MVC 0(2,R2),0(R3) a(pos+1)=a(last+1)
STH R0,0(R3) a(last+1)=w
LA R1,1(R8) pos+1
L R2,NELEM nelem
BAL R14,PERMREV call permrev(pos+1,nelem)
RETNP L R14,SAVENP
BR R14
SAVENP DS A
- ------- ---- -------------------------------------------
PERMREV EQU * permrev(firstix,lastix)
LR R4,R1 xfirst
LR R5,R2 xlast
DO WHILE=(CR,R4,LT,R5) do while(xfirst<xlast)
LR R1,R4 xfirst
SLA R1,1 *2
LA R2,A(R1) @a(xfirst+1)
LR R1,R5 xlast
SLA R1,1 *2
LA R3,A(R1) @a(xlast+1)
LH R0,0(R2) w=a(xfirst+1)
MVC 0(2,R2),0(R3) a(xfirst+1)=a(xlast+1)
STH R0,0(R3) a(xlast+1)=w
LA R4,1(R4) xfirst=xfirst+1
BCTR R5,0 xlast=xlast-1
ENDDO , enddo
BR R14
- ------- ---- ----------------------------------------
FACT EQU * fact(n)
IF C,R1,LE,=F'1' THEN if n<=1 then
LA R0,1 return(1)
ELSE , else
LA R5,1 f=1
LA R2,1 i=1
DO WHILE=(CR,R2,LE,R1) do i=1 to n
MR R4,R2 f*i
LA R2,1(R2) i++
ENDDO , enddo
LR R0,R5 return(f)
ENDIF , endif
BR R14
- ------- ---- -------------------------------------------
SUBFACT EQU * subfact(n)
ST R1,NY n
IF LTR,R1,Z,R1 THEN if n=0 then
LA R0,1 return(1)
ELSE , else
LA R4,1 1
ST R4,TT tt(0)=1
ST R4,IY i=1
DO WHILE=(C,R4,LE,NY) do i=1 to n
L R4,IY i
SRDA R4,32
D R4,=F'2' i/2
IF LTR,R4,Z,R4 THEN if i//2=0 then
LA R0,1 nn=1
ELSE , else
L R0,=F'-1' nn=-1
ENDIF , endif
L R1,IY i
SLA R1,2
L R3,TT-4(R1) tt(i-1)
M R2,IY *i
AR R3,R0 +nn
L R1,IY i
SLA R1,2
ST R3,TT(R1) tt(i)=i*tt(i-1)+nn
L R4,IY i
LA R4,1(R4) i++
ST R4,IY i
ENDDO , enddo
L R1,NY n
SLA R1,2
L R0,TT(R1) return(tt(n))
ENDIF , endif
BR R14
- ---- -------------------------------------------
A DS 12H A work AO DS 12H A origin II DS H COUNT DS H N DS F FPRT DS F flag for printing C DS F D DS X boolean : a(i) different ao(i) FACTNM1 DS F fact(n)-1 NK DS F n in nextper NELEM DS F n elements in nextper NY DS F n in subfact IY DS F i in subfact TT DS 13F tt(0:12) PG1 DC CL44'derangements for the numbers : 1 2 3 4 are :' PG2 DC CL38' table of n counted calculated :' PG3 DC CL36' ----------- ----------- -----------' XDEC DS CL12 temp for xdeco PG DC CL80' ' buffer
YREGS
END DERANGE</lang>
- Output:
derangements for the numbers : 1 2 3 4 are :
2 1 4 3
2 3 4 1
2 4 1 3
3 1 4 2
3 4 1 2
3 4 2 1
4 1 2 3
4 3 1 2
4 3 2 1
table of n counted calculated :
----------- ----------- -----------
0 1 1
1 0 0
2 2 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
!12= 176214841
Ada
<lang Ada>with Ada.Text_IO; use Ada.Text_IO; procedure DePermute is
type U64 is mod 2**64;
type Num is range 0 .. 20;
type NumList is array (Natural range <>) of Num;
type PtNumList is access all NumList;
package IO is new Ada.Text_IO.Integer_IO (Num);
package UIO is new Ada.Text_IO.Modular_IO (U64);
function deranged (depth : Natural; list : PtNumList;
show : Boolean) return U64 is
tmp : Num; count : U64 := 0;
begin
if depth = list'Length then
if show then
for i in list'Range loop IO.Put (list (i), 2); end loop;
New_Line;
end if; return 1;
end if;
for i in reverse depth .. list'Last loop
if Num (i + 1) /= list (depth) then
tmp := list (i); list (i) := list (depth); list (depth) := tmp;
count := count + deranged (depth + 1, list, show);
tmp := list (i); list (i) := list (depth); list (depth) := tmp;
end if;
end loop;
return count;
end deranged;
function gen_n (len : Natural; show : Boolean) return U64 is
list : PtNumList;
begin
list := new NumList (0 .. len - 1);
for i in list'Range loop list (i) := Num (i + 1); end loop;
return deranged (0, list, show);
end gen_n;
function sub_fact (n : Natural) return U64 is begin
if n < 2 then return U64 (1 - n);
else return (sub_fact (n - 1) + sub_fact (n - 2)) * U64 (n - 1);
end if;
end sub_fact;
count : U64;
begin
Put_Line ("Deranged 4:");
count := gen_n (4, True);
Put_Line ("List vs. calc:");
for i in Natural range 0 .. 9 loop
IO.Put (Num (i), 1); UIO.Put (gen_n (i, False), 7);
UIO.Put (sub_fact (i), 7); New_Line;
end loop;
Put_Line ("!20 = " & U64'Image (sub_fact (20)));
end DePermute;</lang>
- Output:
Deranged 4: 4 1 2 3 4 3 1 2 4 3 2 1 3 4 2 1 3 4 1 2 3 1 4 2 2 4 1 3 2 3 4 1 2 1 4 3 List vs. calc: 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Arturo
<lang rebol>isClean?: function [s,o][
loop.with:'i s 'a [
if a = o\[i] -> return false
]
return true
]
derangements: function [n][
original: 1..n
select permutate original 'x ->
isClean? x original
]
subfactorial: function [n].memoize[
(n =< 1)? -> 1 - n
-> (n-1) * (add subfactorial n-1 subfactorial n-2)
]
print "Derangements of 1 2 3 4:" loop derangements 4 'x [
print x
]
print "\nNumber of derangements:" print [pad "n" 5 pad "counted" 15 pad "calculated" 15] print repeat "-" 39 loop 0..9 'z [
counted: size derangements z calculated: subfactorial z print [pad to :string z 5 pad to :string counted 15 pad to :string calculated 15]
]
print ~"\n!20 = |subfactorial 20|"</lang>
- Output:
Derangements of 1 2 3 4:
4 1 2 3
3 1 4 2
3 4 1 2
4 3 1 2
2 1 4 3
2 4 1 3
2 3 4 1
3 4 2 1
4 3 2 1
Number of derangements:
n counted calculated
---------------------------------------
0 1 1
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
!20 = 895014631192902121
AutoHotkey
Note that the permutations are generated in lexicographic order, from http://www.autohotkey.com/forum/topic77959.html <lang AHK>#NoEnv SetBatchLines -1 Process, Priority,, high
output := "Derangements for 1, 2, 3, 4:`n"
obj := [1, 2, 3, 4], objS := obj.Clone() Loop ; permute 4 { obj := perm_NextObj(Obj) If !obj break For k, v in obj if ( objS[k] = v ) continue 2 output .= ObjDisp(obj) "`n" } output .= "`nTable of n, counted, calculated derangements:`n"
Loop 10 ; Count !n { obj := [] count := 0 output .= A_Tab . (i := A_Index-1) . A_Tab Loop % i obj[A_Index] := A_Index objS := obj.Clone() Loop { obj := perm_NextObj(Obj) If !obj break For k, v in obj if ( objS[k] = v ) continue 2 count++ } output .= count . A_Tab . cd(i) . "`n" } output .= "`nApproximation of !20: " . cd(20) MsgBox % Clipboard := output
perm_NextObj(obj){ ; next lexicographic permutation p := 0, objM := ObjMaxIndex(obj) Loop % objM { If A_Index=1 continue t := obj[objM+1-A_Index] n := obj[objM+2-A_Index] If ( t < n ) { p := objM+1-A_Index, pC := obj[p] break } } If !p return false Loop { t := obj[objM+1-A_Index] If ( t > pC ) { n := objM+1-A_Index, nC := obj[n] break } }
obj[n] := pC, obj[p] := nC return ObjReverse(obj, objM-p) }
ObjReverse(Obj, tail){
o := ObjClone(Obj), ObjM := ObjMaxIndex(O) Loop % tail
o[ObjM-A_Index+1] := Obj[ObjM+A_Index-tail]
return o
}
ObjDisp(obj){ For k, v in obj s .= v ", " return SubStr(s, 1, strLen(s)-2) }
cd(n){ ; Count Derangements
static e := 2.71828182845904523536028747135
return n ? floor(ft(n)/e + 1/2) : 1
}
ft(n){ ; FacTorial
a := 1
Loop % n
a *= A_Index
return a
}</lang>
- Output:
Derangements for 1, 2, 3, 4: 2, 1, 4, 3 2, 3, 4, 1 2, 4, 1, 3 3, 1, 4, 2 3, 4, 1, 2 3, 4, 2, 1 4, 1, 2, 3 4, 3, 1, 2 4, 3, 2, 1 Table of n, counted, calculated derangements: 0 0 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 Approximation of !20: 895014631192902144
BBC BASIC
<lang BBC BASIC> PRINT"Derangements for the numbers 0,1,2,3 are:"
Count% = FN_Derangement_Generate(4,TRUE)
PRINT'"Table of n, counted derangements, calculated derangements :"
FOR I% = 0 TO 9
PRINT I%, FN_Derangement_Generate(I%,FALSE), FN_SubFactorial(I%)
NEXT
PRINT'"There is no long int in BBC BASIC!"
PRINT"!20 = ";FN_SubFactorial(20)
END
DEF FN_Derangement_Generate(N%, fPrintOut)
LOCAL A%(), O%(), C%, D%, I%, J%
IF N% = 0 THEN = 1
DIM A%(N%-1), O%(N%-1)
FOR I% = 0 TO N%-1 : A%(I%) = I% : NEXT
O%() = A%()
FOR I% = 0 TO FN_Factorial(DIM(A%(),1)+1)-1
PROC_NextPermutation(A%())
D% = TRUE
FOR J%=0 TO N%-1
IF A%(J%) = O%(J%) THEN D% = FALSE
NEXT
IF D% THEN
C% += 1
IF fPrintOut THEN
FOR K% = 0 TO N%-1
PRINT ;A%(K%);" ";
NEXT
PRINT
ENDIF
ENDIF
NEXT
= C%
DEF PROC_NextPermutation(A%())
LOCAL first, last, elementcount, pos
elementcount = DIM(A%(),1)
IF elementcount < 1 THEN ENDPROC
pos = elementcount-1
WHILE A%(pos) >= A%(pos+1)
pos -= 1
IF pos < 0 THEN
PROC_Permutation_Reverse(A%(), 0, elementcount)
ENDPROC
ENDIF
ENDWHILE
last = elementcount
WHILE A%(last) <= A%(pos)
last -= 1
ENDWHILE
SWAP A%(pos), A%(last)
PROC_Permutation_Reverse(A%(), pos+1, elementcount)
ENDPROC
DEF PROC_Permutation_Reverse(A%(), firstindex, lastindex)
LOCAL first, last
first = firstindex
last = lastindex
WHILE first < last
SWAP A%(first), A%(last)
first += 1
last -= 1
ENDWHILE
ENDPROC
DEF FN_Factorial(N) : IF (N = 1) OR (N = 0) THEN =1 ELSE = N * FN_Factorial(N-1)
DEF FN_SubFactorial(N) : IF N=0 THEN =1 ELSE =N*FN_SubFactorial(N-1)+-1^N
REM Or you could use:
REM DEF FN_SubFactorial(N) : IF N<1 THEN =1 ELSE =(N-1)*(FN_SubFactorial(N-1)+FN_SubFactorial(N-2))</lang>
- Output:
Derangements for the numbers 0,1,2,3 are:
1 0 3 2
1 2 3 0
1 3 0 2
2 0 3 1
2 3 0 1
2 3 1 0
3 0 1 2
3 2 0 1
3 2 1 0
Table of n, counted derangements, calculated derangements :
0 1 1
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
There is no long int in BBC BASIC!
!20 = 8.95014632E17
>
Bracmat
The function calculated-!n has a local variable mem that memoizes already found counts.
This is done by actually updating the function's definition.
The output of the expression lst$calculated-!n demonstrates this.
The function counted-!n is also special: it is designed to always fail, forcing the match operation on the subject !H to assign each element in !H in turn to the sub-pattern (%@?h:~!p), except the element that is equal to !p.
The derangements are built up in the last argument and accumulated in the global variable D.
Also the counter count is a global variable.
<lang bracmat>( ( calculated-!n
= memo answ
. (memo==)
& ( !arg:0&1
| !arg:1&0
| !(memo.):? (!arg.?answ) ?&!answ
| (!arg+-1)
* (calculated-!n$(!arg+-1)+calculated-!n$(!arg+-2))
: ?answ
& (!arg.!answ) !(memo.):?(memo.)
& !answ
)
)
& ( counted-!n
= p P h H A Z L
. !arg:(%?p ?P.?H.?L)
& !H
: ?A
(%@?h:~!p)
(?Z&counted-!n$(!P.!A !Z.!h !L))
| !arg:(..?L)
& 1+!count:?count
& (!count.!L) !D:?D
& ~
)
& out$"Derangements of 1 2 3 4" & :?D & 0:?count & ( counted-!n$(4 3 2 1.4 3 2 1.)
| out$!D )
& ( pad
= len w
. @(!arg:? [?len)
& @(" ":? [!len ?w)
& !w !arg
)
& :?K & -1:?N & out$(str$(N pad$List pad$Calc)) & whl
' ( !N+1:<10:?N
& ( 0:?count
& :?D
& counted-!n$(!K.!K.)
| out$(str$(!N pad$!count pad$(calculated-!n$!N)))
)
& !N !K:?K
)
& out$("!20 =" calculated-!n$20) & lst$calculated-!n )</lang>
- Output:
Derangements of 1 2 3 4
(9.4 3 2 1)
(8.3 4 2 1)
(7.2 3 4 1)
(6.4 3 1 2)
(5.3 4 1 2)
(4.3 1 4 2)
(3.2 4 1 3)
(2.4 1 2 3)
(1.2 1 4 3)
N List Calc
0 1 1
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
!20 = 895014631192902121
(calculated-!n=
memo answ
. ( memo
=
= (20.895014631192902121)
(19.44750731559645106)
(18.2355301661033953)
(17.130850092279664)
(16.7697064251745)
(15.481066515734)
(14.32071101049)
(13.2290792932)
(12.176214841)
(11.14684570)
(10.1334961)
(9.133496)
(8.14833)
(7.1854)
(6.265)
(5.44)
(4.9)
(3.2)
(2.1)
)
& ( !arg:0&1
| !arg:1&0
| !(memo.):? (!arg.?answ) ?&!answ
| (!arg+-1)*(calculated-!n$(!arg+-1)+calculated-!n$(!arg+-2))
: ?answ
& (!arg.!answ) !(memo.):?(memo.)
& !answ
)
);
C
<lang C>#include <stdio.h> typedef unsigned long long LONG;
LONG deranged(int depth, int len, int *d, int show) {
int i;
char tmp;
LONG count = 0;
if (depth == len) {
if (show) {
for (i = 0; i < len; i++) putchar(d[i] + 'a');
putchar('\n');
}
return 1;
}
for (i = len - 1; i >= depth; i--) {
if (i == d[depth]) continue;
tmp = d[i]; d[i] = d[depth]; d[depth] = tmp;
count += deranged(depth + 1, len, d, show);
tmp = d[i]; d[i] = d[depth]; d[depth] = tmp;
}
return count;
}
LONG gen_n(int n, int show) {
LONG i;
int a[1024]; /* 1024 ought to be big enough for anybody */
for (i = 0; i < n; i++) a[i] = i;
return deranged(0, n, a, show);
}
LONG sub_fact(int n) {
return n < 2 ? 1 - n : (sub_fact(n - 1) + sub_fact(n - 2)) * (n - 1);
}
int main() {
int i;
printf("Deranged Four:\n");
gen_n(4, 1);
printf("\nCompare list vs calc:\n");
for (i = 0; i < 10; i++)
printf("%d:\t%llu\t%llu\n", i, gen_n(i, 0), sub_fact(i));
printf("\nfurther calc:\n");
for (i = 10; i <= 20; i++)
printf("%d: %llu\n", i, sub_fact(i));
return 0;
}</lang>
- Output:
Deranged Four: dabc dcab dcba cdba cdab cadb bdac bcda badc Compare list vs calc: 0: 1 1 1: 0 0 2: 1 1 3: 2 2 4: 9 9 5: 44 44 6: 265 265 7: 1854 1854 8: 14833 14833 9: 133496 133496 further calc: 10: 1334961 11: 14684570 12: 176214841 13: 2290792932 14: 32071101049 15: 481066515734 16: 7697064251745 17: 130850092279664 18: 2355301661033953 19: 44750731559645106 20: 895014631192902121
C#
Recursive version
<lang csharp> using System; class Derangements {
static int n = 4; static int [] buf = new int [n]; static bool [] used = new bool [n];
static void Main()
{
for (int i = 0; i < n; i++) used [i] = false;
rec(0);
}
static void rec(int ind)
{
for (int i = 0; i < n; i++)
{
if (!used [i] && i != ind)
{
used [i] = true;
buf [ind] = i;
if (ind + 1 < n) rec(ind + 1);
else Console.WriteLine(string.Join(",", buf));
used [i] = false;
} } }
} </lang>
Clojure
Generating functions with no fixed point
<lang Clojure>(ns derangements.core
(:require [clojure.set :as s]))
(defn subfactorial [n]
(case n 0 1 1 0 (* (dec n) (+ (subfactorial (dec n)) (subfactorial (- n 2))))))
(defn no-fixed-point
"f : A -> B must be a biyective function written as a hash-map, returns
all g : A -> B such that (f(a) = b) => not(g(a) = b)"
[f]
(case (count f)
0 [{}]
1 []
(let [g (s/map-invert f)
a (first (keys f))
a' (f a)]
(mapcat
(fn [b'] (let [b (g b')
f' (dissoc f a b)]
(concat (map #(reduce conj % [[a b'] [b a']])
(no-fixed-point f'))
(map #(conj % [a b'])
(no-fixed-point (assoc f' b a'))))))
(filter #(not= a' %) (keys g))))))
(defn derangements [xs]
{:pre [(= (count xs) (count (set xs)))]}
(map (fn [f] (mapv f xs))
(no-fixed-point (into {} (map vector xs xs)))))
(defn -main []
(do
(doall (map println (derangements [0,1,2,3])))
(doall (map #(println (str (subfactorial %) " " (count (derangements (range %)))))
(range 10)))
(println (subfactorial 20))))
</lang>
- Output:
[1 0 3 2] [1 2 3 0] [1 3 0 2] [2 3 0 1] [2 3 1 0] [2 0 3 1] [3 2 1 0] [3 2 0 1] [3 0 1 2] 1 1 0 0 1 1 2 2 9 9 44 44 265 265 1854 1854 14833 14833 133496 133496 895014631192902121
D
Iterative Version
<lang d>import std.stdio, std.algorithm, std.typecons, std.conv,
std.range, std.traits;
T factorial(T)(in T n) pure nothrow @safe @nogc {
Unqual!T result = 1;
foreach (immutable i; 2 .. n + 1)
result *= i;
return result;
}
T subfact(T)(in T n) pure nothrow @safe @nogc {
if (0 <= n && n <= 2)
return n != 1;
return (n - 1) * (subfact(n - 1) + subfact(n - 2));
}
auto derangements(in size_t n, in bool countOnly=false) pure nothrow @safe {
size_t[] seq = n.iota.array; auto ori = seq.idup; size_t[][] all; size_t cnt = n == 0;
foreach (immutable tot; 0 .. n.factorial - 1) {
size_t j = n - 2;
while (seq[j] > seq[j + 1])
j--;
size_t k = n - 1;
while (seq[j] > seq[k])
k--;
seq[k].swap(seq[j]);
size_t r = n - 1;
size_t s = j + 1;
while (r > s) {
seq[s].swap(seq[r]);
r--;
s++;
}
j = 0;
while (j < n && seq[j] != ori[j])
j++;
if (j == n) {
if (countOnly)
cnt++;
else
all ~= seq.dup;
}
}
return tuple(all, cnt);
}
void main() @safe {
"Derangements for n = 4:".writeln;
foreach (const d; 4.derangements[0])
d.writeln;
"\nTable of n vs counted vs calculated derangements:".writeln;
foreach (immutable i; 0 .. 10)
writefln("%s %-7s%-7s", i, derangements(i, 1)[1], i.subfact);
writefln("\n!20 = %s", 20L.subfact);
}</lang>
- Output:
Derangements for n = 4: [1, 0, 3, 2] [1, 2, 3, 0] [1, 3, 0, 2] [2, 0, 3, 1] [2, 3, 0, 1] [2, 3, 1, 0] [3, 0, 1, 2] [3, 2, 0, 1] [3, 2, 1, 0] Table of n vs counted vs calculated derangements: 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Recursive Version
Slightly slower but more compact recursive version of the derangements function, based on the D entry of the permutations task. Same output. <lang d>import std.stdio, std.algorithm, std.typecons, std.conv, std.range;
T factorial(T)(in T n) pure nothrow {
Unqual!T result = 1;
foreach (immutable i; 2 .. n + 1)
result *= i;
return result;
}
T subfact(T)(in T n) pure nothrow {
if (0 <= n && n <= 2)
return n != 1;
return (n - 1) * (subfact(n - 1) + subfact(n - 2));
}
auto derangementsR(in size_t n, in bool countOnly=false) pure /*nothrow*/ {
auto seq = n.iota.array; immutable ori = seq.idup; const(size_t[])[] res; size_t cnt;
void perms(in size_t[] s, in size_t[] pre=null) /*nothrow*/ {
if (s.length) {
foreach (immutable i, immutable c; s)
perms(s[0 .. i] ~ s[i + 1 .. $], pre ~ c);
} else if (zip(pre, ori).all!(po => po[0] != po[1])) {
if (countOnly) cnt++;
else res ~= pre;
}
}
perms(seq); return tuple(res, cnt);
}
void main() {
"Derangements for n = 4:".writeln;
foreach (const d; 4.derangementsR[0])
d.writeln;
"\nTable of n vs counted vs calculated derangements:".writeln;
foreach (immutable i; 0 .. 10)
writefln("%s %-7s%-7s", i, derangementsR(i, 1)[1], i.subfact);
writefln("\n!20 = %s", 20L.subfact);
}</lang>
EchoLisp
<lang scheme> (lib 'list) ;; in-permutations (lib 'bigint)
- generates derangements by filtering out permutations
(define (derangement? nums) ;; predicate
(for/and ((n nums) (i (length nums))) (!= n i)))
(define (derangements n)
(for/list ((p (in-permutations n))) #:when (derangement? p) p))
(define (count-derangements n)
(for/sum ((p (in-permutations n))) #:when (derangement? p) 1))
- !n = (n - 1) (!(n-1) + !(n-2))
(define (!n n) (* (1- n) (+ (!n (1- n)) (!n (- n 2))))) (remember '!n #(1 0))
</lang>
- Output:
<lang scheme> (derangements 4)
→ ((3 0 1 2) (2 0 3 1) (2 3 0 1) (3 2 0 1) (3 2 1 0) (2 3 1 0) (1 2 3 0) (1 3 0 2) (1 0 3 2))
- generated versus computed
(for ((i 10)) (writeln i '| (count-derangements i) (!n i)))
0 | 1 1 1 | 0 0 2 | 1 1 3 | 2 2 4 | 9 9 5 | 44 44 6 | 265 265 7 | 1854 1854 8 | 14833 14833 9 | 133496 133496
(!n 20)
→ 895014631192902121
</lang>
Elixir
<lang elixir>defmodule Permutation do
def derangements(n) do
list = Enum.to_list(1..n)
Enum.filter(permutation(list), fn perm ->
Enum.zip(list, perm) |> Enum.all?(fn {a,b} -> a != b end)
end)
end
def subfact(0), do: 1
def subfact(1), do: 0
def subfact(n), do: (n-1) * (subfact(n-1) + subfact(n-2))
def permutation([]), do: [[]]
def permutation(list) do
for x <- list, y <- permutation(list -- [x]), do: [x|y]
end
end
IO.puts "derangements for n = 4" Enum.each(Permutation.derangements(4), &IO.inspect &1)
IO.puts "\nNumber of derangements" IO.puts " n derange subfact" Enum.each(0..9, fn n ->
:io.format "~2w :~9w,~9w~n", [n, length(Permutation.derangements(n)), Permutation.subfact(n)]
end) Enum.each(10..20, fn n ->
:io.format "~2w :~19w~n", [n, Permutation.subfact(n)]
end)</lang>
- Output:
derangements for n = 4 [2, 1, 4, 3] [2, 3, 4, 1] [2, 4, 1, 3] [3, 1, 4, 2] [3, 4, 1, 2] [3, 4, 2, 1] [4, 1, 2, 3] [4, 3, 1, 2] [4, 3, 2, 1] Number of derangements n derange subfact 0 : 1, 1 1 : 0, 0 2 : 1, 1 3 : 2, 2 4 : 9, 9 5 : 44, 44 6 : 265, 265 7 : 1854, 1854 8 : 14833, 14833 9 : 133496, 133496 10 : 1334961 11 : 14684570 12 : 176214841 13 : 2290792932 14 : 32071101049 15 : 481066515734 16 : 7697064251745 17 : 130850092279664 18 : 2355301661033953 19 : 44750731559645106 20 : 895014631192902121
F#
The Function
<lang fsharp> // Generate derangements. Nigel Galloway: July 9th., 2019 let derange n=
let fG n i g=let e=Array.copy n in e.[i]<-n.[g]; e.[g]<-n.[i]; e
let rec derange n g α=seq{
match (α>0,n&&&(1<<<α)=0) with
(true,true)->for i in [0..α-1] do if n&&&(1<<<i)=0 then let g=(fG g α i) in yield! derange (n+(1<<<i)) g (α-1); yield! derange n g (α-1)
|(true,false)->yield! derange n g (α-1)
|(false,false)->yield g
|_->()}
derange 0 [|1..n|] (n-1)
</lang>
The Task
<lang fsharp> derange 4 |> Seq.iter(printfn "%A") </lang>
- Output:
[|4; 3; 2; 1|] [|2; 3; 4; 1|] [|3; 4; 2; 1|] [|3; 4; 1; 2|] [|4; 3; 1; 2|] [|3; 1; 4; 2|] [|2; 1; 4; 3|] [|2; 4; 1; 3|] [|4; 1; 2; 3|]
<lang fsharp> let subFact n=let rec fN n g=match n with 0m->int64(round(g/2.7182818284590452353602874713526624978m))|_->fN (n-1m) (g*n) in if n=0 then 1L else fN (decimal n) 1m [1..9] |> Seq.iter(fun n->printfn "items=%d !n=%d derangements=%d" n (subFact n) (derange n|>Seq.length)) </lang>
- Output:
items=1 !n=0 derangements=0 items=2 !n=1 derangements=1 items=3 !n=2 derangements=2 items=4 !n=9 derangements=9 items=5 !n=44 derangements=44 items=6 !n=265 derangements=265 items=7 !n=1854 derangements=1854 items=8 !n=14833 derangements=14833 items=9 !n=133496 derangements=133496
Factor
<lang factor>USING: combinators formatting io kernel math math.combinatorics prettyprint sequences ; IN: rosetta-code.derangements
- !n ( n -- m )
{
{ 0 [ 1 ] }
{ 1 [ 0 ] }
[ [ 1 - !n ] [ 2 - !n + ] [ 1 - * ] tri ]
} case ;
- derangements ( n -- seq )
<iota> dup [ [ = ] 2map [ f = ] all? ] with filter-permutations ;
"4 derangements" print 4 derangements . nl "n count calc\n= ====== ======" print 10 <iota> [
dup [ derangements length ] [ !n ] bi "%d%8d%8d\n" printf
] each nl "!20 = " write 20 !n .</lang>
- Output:
4 derangements
V{
{ 1 0 3 2 }
{ 1 2 3 0 }
{ 1 3 0 2 }
{ 2 0 3 1 }
{ 2 3 0 1 }
{ 2 3 1 0 }
{ 3 0 1 2 }
{ 3 2 0 1 }
{ 3 2 1 0 }
}
n count calc
= ====== ======
0 1 1
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
!20 = 895014631192902121
FreeBASIC
<lang freebasic>' version 08-04-2017 ' compile with: fbc -s console
Sub Subfactorial(a() As ULongInt)
Dim As ULong i Dim As ULongInt num
For i = 0 To UBound(a)
num = num * i
If (i And 1) = 1 Then
num -= 1
Else
num += 1
End If
a(i) = num
Next
End Sub
' Heap's algorithm non-recursive Function perms_derange(n As ULong, flag As Long = 0) As ULongInt
' fast upto n < 12 If n = 0 Then Return 1
Dim As ULong i, j, c1, count Dim As ULong a(0 To n -1), c(0 To n -1)
For j = 0 To n -1
a(j) = j
Next
While i < n
If c(i) < i Then
If (i And 1) = 0 Then
Swap a(0), a(i)
Else
Swap a(c(i)), a(i)
End If
For j = 0 To n -1
If a(j) = j Then j = 99
Next
If j < 99 Then
count += 1
If flag = 0 Then
c1 += 1
For j = 0 To n -1
Print a(j);
Next
If c1 > 12 Then
Print : c1 = 0
Else
Print " ";
End If
End If
End If
c(i) += 1
i = 0
Else
c(i) = 0
i += 1
End If
Wend
If flag = 0 AndAlso c1 <> 0 Then Print
Return count
End Function
' ------=< MAIN >=------
Dim As ULong i, n = 4 Dim As ULongInt subfac(20)
Subfactorial(subfac())
Print "permutations derangements for n = "; n i = perms_derange(n) Print "count returned = "; i; " , !"; n; " calculated = "; subfac(n)
Print Print "count counted subfactorial" Print "---------------------------" For i = 0 To 9
Print Using " ###: ######## ########"; i; perms_derange(i, 1); subfac(i)
Next For i = 10 To 20
Print Using " ###: ###################"; i; subfac(i)
Next
' empty keyboard buffer While InKey <> "" : Wend Print : Print "hit any key to end program" Sleep End</lang>
- Output:
permutations derangements for n = 4 1302 3012 1032 2031 2301 3201 3210 2310 1230 count returned = 9 , !4 calculated = 9 count counted subfactorial --------------------------- 0: 1 1 1: 0 0 2: 1 1 3: 2 2 4: 9 9 5: 44 44 6: 265 265 7: 1854 1854 8: 14833 14833 9: 133496 133496 10: 1334961 11: 14684570 12: 176214841 13: 2290792932 14: 32071101049 15: 481066515734 16: 7697064251745 17: 130850092279664 18: 2355301661033953 19: 44750731559645106 20: 895014631192902121
GAP
<lang gap># All of this is built-in Derangements([1 .. 4]);
- [ [ 2, 1, 4, 3 ], [ 2, 3, 4, 1 ], [ 2, 4, 1, 3 ], [ 3, 1, 4, 2 ], [ 3, 4, 1, 2 ], [ 3, 4, 2, 1 ],
- [ 4, 1, 2, 3 ], [ 4, 3, 1, 2 ], [ 4, 3, 2, 1 ] ]
Size(last);
- 9
NrDerangements([1 .. 4]);
- 9
- An implementation using formula D(n + 1) = n*(D(n) + D(n - 1))
NrDerangementsAlt_memo := [1, 0]; NrDerangementsAlt := function(n) if not IsBound(NrDerangementsAlt_memo[n + 1]) then NrDerangementsAlt_memo[n + 1] := (n - 1)*(NrDerangementsAlt(n - 1) + NrDerangementsAlt(n - 2)); fi; return NrDerangementsAlt_memo[n + 1]; end;
L := List([0 .. 9]);
PrintArray(TransposedMat([L, List(L, n -> Size(Derangements([1 .. n]))), List(L, n -> NrDerangements([1 .. n])), List(L, NrDerangementsAlt)]));
- [ [ 0, 1, 1, 1 ],
- [ 1, 0, 0, 0 ],
- [ 2, 1, 1, 1 ],
- [ 3, 2, 2, 2 ],
- [ 4, 9, 9, 9 ],
- [ 5, 44, 44, 44 ],
- [ 6, 265, 265, 265 ],
- [ 7, 1854, 1854, 1854 ],
- [ 8, 14833, 14833, 14833 ],
- [ 9, 133496, 133496, 133496 ] ]</lang>
Go
<lang go>package main
import (
"fmt" "math/big"
)
// task 1: function returns list of derangements of n integers func dList(n int) (r [][]int) {
a := make([]int, n)
for i := range a {
a[i] = i
}
// recursive closure permutes a
var recurse func(last int)
recurse = func(last int) {
if last == 0 {
// bottom of recursion. you get here once for each permutation.
// test if permutation is deranged.
for j, v := range a {
if j == v {
return // no, ignore it
}
}
// yes, save a copy
r = append(r, append([]int{}, a...))
return
}
for i := last; i >= 0; i-- {
a[i], a[last] = a[last], a[i]
recurse(last - 1)
a[i], a[last] = a[last], a[i]
}
}
recurse(n - 1)
return
}
// task 3: function computes subfactorial of n func subFact(n int) *big.Int {
if n == 0 {
return big.NewInt(1)
} else if n == 1 {
return big.NewInt(0)
}
d0 := big.NewInt(1)
d1 := big.NewInt(0)
f := new(big.Int)
for i, n64 := int64(1), int64(n); i < n64; i++ {
d0, d1 = d1, d0.Mul(f.SetInt64(i), d0.Add(d0, d1))
}
return d1
}
func main() {
// task 2:
fmt.Println("Derangements of 4 integers")
for _, d := range dList(4) {
fmt.Println(d)
}
// task 4:
fmt.Println("\nNumber of derangements")
fmt.Println("N Counted Calculated")
for n := 0; n <= 9; n++ {
fmt.Printf("%d %8d %11s\n", n, len(dList(n)), subFact(n).String())
}
// stretch (sic)
fmt.Println("\n!20 =", subFact(20))
}</lang>
- Output:
Derangements of 4 integers [1 0 3 2] [3 0 1 2] [1 3 0 2] [2 0 3 1] [2 3 0 1] [3 2 0 1] [3 2 1 0] [2 3 1 0] [1 2 3 0] Number of derangements N Counted Calculated 0 0 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Groovy
Solution: <lang groovy>def fact = { n -> [1,(1..<(n+1)).inject(1) { prod, i -> prod * i }].max() } def subfact subfact = { BigInteger n -> (n == 0) ? 1 : (n == 1) ? 0 : ((n-1) * (subfact(n-1) + subfact(n-2))) }
def derangement = { List l ->
def d = []
if (l) l.eachPermutation { p -> if ([p,l].transpose().every{ pp, ll -> pp != ll }) d << p }
d
}</lang>
Test: <lang groovy>def d = derangement([1,2,3,4]) assert d.size() == subfact(4) d.each { println it }
println """ n # derangements subfactorial = ============== ============""" (0..9). each { n ->
def dr = derangement((1..<(n+1)) as List)
def sf = subfact(n)
printf('%1d %14d %12d\n', n, dr.size(), sf)
}
println """ !20 == ${subfact(20)} """</lang>
- Output:
[2, 1, 4, 3] [2, 3, 4, 1] [2, 4, 1, 3] [3, 1, 4, 2] [3, 4, 1, 2] [3, 4, 2, 1] [4, 1, 2, 3] [4, 3, 1, 2] [4, 3, 2, 1] n # derangements subfactorial = ============== ============ 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 == 895014631192902121
Haskell
<lang Haskell>import Control.Monad (forM_)
import Data.List (permutations)
-- Compute all derangements of a list derangements
:: Eq a => [a] -> a
derangements = (\x -> filter (and . zipWith (/=) x)) <*> permutations
-- Compute the number of derangements of n elements subfactorial
:: (Eq a, Num a) => a -> a
subfactorial 0 = 1 subfactorial 1 = 0 subfactorial n = (n - 1) * (subfactorial (n - 1) + subfactorial (n - 2))
main :: IO () main -- Generate and show all the derangements of four integers
= do
print $ derangements [1 .. 4]
putStrLn ""
-- Print the count of derangements vs subfactorial
forM_ [1 .. 9] $
\i ->
putStrLn $
mconcat
[show (length (derangements [1 .. i])), " ", show (subfactorial i)]
putStrLn ""
-- Print the number of derangements in a list of 20 items
print $ subfactorial 20</lang>
- Output:
[[4,3,2,1],[3,4,2,1],[2,3,4,1],[4,1,2,3],[2,4,1,3],[2,1,4,3],[4,3,1,2],[3,4,1,2],[3,1,4,2]] 0 0 1 1 2 2 9 9 44 44 265 265 1854 1854 14833 14833 133496 133496 895014631192902121
Alternatively, this is a backtracking method:
<lang haskell>derangements xs = loop xs xs
where loop [] [] = [[]]
loop (h:hs) xs = [x:ys | x <- xs, x /= h, ys <- loop hs (delete x xs)]</lang>
Since the value i cannot occur in position i, we prefix i on all other derangements from 1 to n that do not include i. The first method of filtering permutations is significantly faster, in practice, however.
J
Note: !n in J denotes factorial (or gamma n+1), and not subfactorial.
<lang j>derangement=: (A.&i.~ !)~ (*/ .~: # [) i. NB. task item 1 subfactorial=: ! * +/@(_1&^ % !)@i.@>: NB. task item 3</lang>
Requested examples:
<lang j> derangement 4 NB. task item 2 1 0 3 2 1 2 3 0 1 3 0 2 2 0 3 1 2 3 0 1 2 3 1 0 3 0 1 2 3 2 0 1 3 2 1 0
(,subfactorial,#@derangement)"0 i.10 NB. task item 4
0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496
subfactorial 20 NB. stretch task
8.95015e17
subfactorial 20x NB. using extended precision
895014631192902121</lang>
Note that derangement 10 was painfully slow (almost 3 seconds, about 10 times slower than derangement 9 and 100 times slower than derangement 8) -- this is a brute force approach. But brute force seems like an appropriate solution here, since factorial divided by subfactorial asymptotically approaches a value near 0.367879 (the reciprocal of e).
Java
<lang java>import java.util.ArrayList; import java.util.Arrays; import java.util.List;
public class Derangement {
public static void main(String[] args) {
System.out.println("derangements for n = 4\n");
for (Object d : (ArrayList)(derangements(4, false)[0])) {
System.out.println(Arrays.toString((int[])d));
}
System.out.println("\ntable of n vs counted vs calculated derangements\n");
for (int i = 0; i < 10; i++) {
int d = ((Integer)derangements(i, true)[1]).intValue();
System.out.printf("%d %-7d %-7d\n", i, d, subfact(i));
}
System.out.printf ("\n!20 = %20d\n", subfact(20L));
}
static Object[] derangements(int n, boolean countOnly) {
int[] seq = iota(n);
int[] ori = Arrays.copyOf(seq, n);
long tot = fact(n);
List<int[]> all = new ArrayList<int[]>();
int cnt = n == 0 ? 1 : 0;
while (--tot > 0) {
int j = n - 2;
while (seq[j] > seq[j + 1]) {
j--;
}
int k = n - 1;
while (seq[j] > seq[k]) {
k--;
}
swap(seq, k, j);
int r = n - 1;
int s = j + 1;
while (r > s) {
swap(seq, s, r);
r--;
s++;
}
j = 0;
while (j < n && seq[j] != ori[j]) {
j++;
}
if (j == n) {
if (countOnly) {
cnt++;
} else {
all.add(Arrays.copyOf(seq, n));
}
}
}
return new Object[]{all, cnt};
}
static long fact(long n) {
long result = 1;
for (long i = 2; i <= n; i++) {
result *= i;
}
return result;
}
static long subfact(long n) {
if (0 <= n && n <= 2) {
return n != 1 ? 1 : 0;
}
return (n - 1) * (subfact(n - 1) + subfact(n - 2));
}
static void swap(int[] arr, int lhs, int rhs) {
int tmp = arr[lhs];
arr[lhs] = arr[rhs];
arr[rhs] = tmp;
}
static int[] iota(int n) {
if (n < 0) {
throw new IllegalArgumentException("iota cannot accept < 0");
}
int[] r = new int[n];
for (int i = 0; i < n; i++) {
r[i] = i;
}
return r;
}
}</lang>
derangements for n = 4 [1, 0, 3, 2] [1, 2, 3, 0] [1, 3, 0, 2] [2, 0, 3, 1] [2, 3, 0, 1] [2, 3, 1, 0] [3, 0, 1, 2] [3, 2, 0, 1] [3, 2, 1, 0] table of n vs counted vs calculated derangements 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
jq
The following implementation of "derangements" generates the derangements directly, without generating all permutations. Since recent versions of jq have tail-call optimization (TCO) for arity-0 recursive functions, the workhorse inner function (deranged/0) is implemented as an arity-0 function. <lang jq>def derangements:
# In order to reference the original array conveniently, define _derangements(ary):
def _derangements(ary):
# We cannot put the i-th element in the i-th place:
def deranged: # state: [i, available]
.[0] as $i | .[1] as $in
| if $i == (ary|length) then []
else
($in[] | select (. != ary[$i])) as $j
| [$j] + ([$i+1, ($in - [$j])] | deranged)
end
;
[0,ary]|deranged;
. as $in | _derangements($in);
def subfact:
if . == 0 then 1 elif . == 1 then 0 else (.-1) * (((.-1)|subfact) + ((.-2)|subfact)) end;
- Avoid creating an array just to count the items in a stream:
def count(g): reduce g as $i (0; . + 1);</lang> Tasks: <lang jq> "Derangements:",
([range(1;5)] | derangements), "", "Counted vs Computed Derangments:", (range(1;10) as $i | "\($i): \(count( [range(0;$i)] | derangements)) vs \($i|subfact)"), "", "Computed approximation to !20 (15 significant digits): \(20|subfact)"</lang>
- Output:
<lang sh>$ jq -n -c -r -f derangements.jq jq -n -c -r -f derangements.jq
Derangements: [2,1,4,3] [2,3,4,1] [2,4,1,3] [3,1,4,2] [3,4,1,2] [3,4,2,1] [4,1,2,3] [4,3,1,2] [4,3,2,1]
Counted vs Computed Derangments: 1: 0 vs 0 2: 1 vs 1 3: 2 vs 2 4: 9 vs 9 5: 44 vs 44 6: 265 vs 265 7: 1854 vs 1854 8: 14833 vs 14833 9: 133496 vs 133496
Computed approximation to !20 (15 significant digits): 895014631192902000</lang>
Julia
<lang julia>using Printf, Combinatorics
derangements(n::Int) = (perm for perm in permutations(1:n)
if all(indx != p for (indx, p) in enumerate(perm)))
function subfact(n::Integer)::Integer
if n in (0, 2)
return 1
elseif n == 1
return 0
elseif 1 ≤ n ≤ 18
return round(Int, factorial(n) / e)
elseif n > 0
return (n - 1) * ( subfact(n - 1) + subfact(n - 2) )
else
error()
end
end
println("Derangements of [1, 2, 3, 4]") for perm in derangements(4)
println(perm)
end
@printf("\n%5s%13s%13s\n", "n", "derangements", "!n") for n in 1:10
ders = derangements(n)
subf = subfact(n)
@printf("%5i%13i%13i\n", n, length(collect(ders)), subf)
end
println("\n!20 = ", subfact(20))</lang>
- Output:
Derangements of [1, 2, 3, 4]
[2, 1, 4, 3]
[2, 3, 4, 1]
[2, 4, 1, 3]
[3, 1, 4, 2]
[3, 4, 1, 2]
[3, 4, 2, 1]
[4, 1, 2, 3]
[4, 3, 1, 2]
[4, 3, 2, 1]
n derangements !n
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
10 1334961 1334961
!20 = 895014631192902121
Kotlin
<lang scala>// version 1.1.2
fun <T> permute(input: List<T>): List<List<T>> {
if (input.size == 1) return listOf(input)
val perms = mutableListOf<List<T>>()
val toInsert = input[0]
for (perm in permute(input.drop(1))) {
for (i in 0..perm.size) {
val newPerm = perm.toMutableList()
newPerm.add(i, toInsert)
perms.add(newPerm)
}
}
return perms
}
fun derange(input: List<Int>): List<List<Int>> {
if (input.isEmpty()) return listOf(input)
return permute(input).filter { permutation ->
permutation.filterIndexed { i, index -> i == index }.none()
}
}
fun subFactorial(n: Int): Long =
when (n) {
0 -> 1
1 -> 0
else -> (n - 1) * (subFactorial(n - 1) + subFactorial(n - 2))
}
fun main(args: Array<String>) {
val input = listOf(0, 1, 2, 3)
val derangements = derange(input)
println("There are ${derangements.size} derangements of $input, namely:\n")
derangements.forEach(::println)
println("\nN Counted Calculated")
println("- ------- ----------")
for (n in 0..9) {
val list = List(n) { it }
val counted = derange(list).size
println("%d %-9d %-9d".format(n, counted, subFactorial(n)))
}
println("\n!20 = ${subFactorial(20)}")
}</lang>
- Output:
There are 9 derangements of [0, 1, 2, 3], namely: [1, 2, 3, 0] [2, 0, 3, 1] [2, 3, 0, 1] [2, 3, 1, 0] [1, 0, 3, 2] [1, 3, 0, 2] [3, 0, 1, 2] [3, 2, 0, 1] [3, 2, 1, 0] N Counted Calculated - ------- ---------- 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Lua
<lang Lua>-- Return an iterator to produce every permutation of list function permute (list)
local function perm (list, n)
if n == 0 then coroutine.yield(list) end
for i = 1, n do
list[i], list[n] = list[n], list[i]
perm(list, n - 1)
list[i], list[n] = list[n], list[i]
end
end
return coroutine.wrap(function() perm(list, #list) end)
end
-- Return a copy of table t (wouldn't work for a table of tables) function copy (t)
if not t then return nil end
local new = {}
for k, v in pairs(t) do new[k] = v end
return new
end
-- Return true if no value in t1 can be found at the same index of t2 function noMatches (t1, t2)
for k, v in pairs(t1) do
if t2[k] == v then return false end
end
return true
end
-- Return a table of all derangements of table t function derangements (t)
local orig = copy(t)
local nextPerm, deranged = permute(t), {}
local numList, keep = copy(nextPerm())
while numList do
if noMatches(numList, orig) then table.insert(deranged, numList) end
numList = copy(nextPerm())
end
return deranged
end
-- Return the subfactorial of n function subFact (n)
if n < 2 then
return 1 - n
else
return (subFact(n - 1) + subFact(n - 2)) * (n - 1)
end
end
-- Return a table of the numbers 1 to n function listOneTo (n)
local t = {}
for i = 1, n do t[i] = i end
return t
end
-- Main procedure print("Derangements of [1,2,3,4]") for k, v in pairs(derangements(listOneTo(4))) do print("", unpack(v)) end print("\n\nSubfactorial vs counted derangements\n") print("\tn\t| subFact(n)\t| Derangements") print(" " .. string.rep("-", 42)) for i = 0, 9 do
io.write("\t" .. i .. "\t| " .. subFact(i))
if string.len(subFact(i)) < 5 then io.write("\t") end
print("\t| " .. #derangements(listOneTo(i)))
end print("\n\nThe subfactorial of 20 is " .. subFact(20))</lang>
- Output:
Derangements of [1,2,3,4]
2 3 4 1
3 4 2 1
4 3 2 1
4 3 1 2
3 4 1 2
3 1 4 2
2 4 1 3
4 1 2 3
2 1 4 3
Subfactorial vs counted derangements
n | subFact(n) | Derangements
------------------------------------------
0 | 1 | 1
1 | 0 | 0
2 | 1 | 1
3 | 2 | 2
4 | 9 | 9
5 | 44 | 44
6 | 265 | 265
7 | 1854 | 1854
8 | 14833 | 14833
9 | 133496 | 133496
The subfactorial of 20 is 8.950146311929e+17
Mathematica/Wolfram Language
<lang Mathematica> Needs["Combinatorica`"] derangements[n_] := Derangements[Range[n]] derangements[4] Table[{NumberOfDerangements[i], Subfactorial[i]}, {i, 9}] // TableForm Subfactorial[20]</lang>
- Output:
{{2, 1, 4, 3}, {2, 3, 4, 1}, {2, 4, 1, 3}, {3, 1, 4, 2}, {3, 4, 1, 2},
{3, 4, 2, 1}, {4, 1, 2, 3}, {4, 3, 1, 2}, {4, 3, 2, 1}}
0 0
1 1
2 2
9 9
44 44
265 265
1854 1854
14833 14833
133496 133496
895014631192902121
Nim
<lang Nim>import algorithm, sequtils, strformat, strutils, tables
iterator derangements[T](a: openArray[T]): seq[T] =
var perm = @a
while true:
if not perm.nextPermutation():
break
block checkDerangement:
for i, val in a:
if perm[i] == val: break checkDerangement
yield perm
proc `!`(n: Natural): Natural =
if n <= 1: return 1 - n result = (n - 1) * (!(n - 1) + !(n - 2))
echo "Derangements of 1 2 3 4:" for d in [1, 2, 3, 4].derangements():
echo d.join(" ")
echo "\nNumber of derangements:" echo "n counted calculated" echo "- ------- ----------" for n in 0..9:
echo &"{n} {toSeq(derangements(toSeq(1..n))).len:>6} {!n:>6}"
echo "\n!20 = ", !20</lang>
- Output:
Derangements of 1 2 3 4: 2 1 4 3 2 3 4 1 2 4 1 3 3 1 4 2 3 4 1 2 3 4 2 1 4 1 2 3 4 3 1 2 4 3 2 1 Number of derangements: n counted calculated - ------- ---------- 0 0 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
PARI/GP
<lang parigp>derangements(n)=if(n,round(n!/exp(1)),1); derange(n)={ my(v=[[]],tmp); for(level=1,n, tmp=List(); for(i=1,#v, for(k=1,n, if(k==level, next); for(j=1,level-1,if(v[i][j]==k, next(2))); listput(tmp, concat(v[i],k)) ) ); v=Vec(tmp) ); v }; derange(4) for(n=0,9,print("!"n" = "#derange(n)" = "derangements(n))) derangements(20)</lang>
- Output:
%1 = [[2, 1, 4, 3], [2, 3, 4, 1], [2, 4, 1, 3], [3, 1, 4, 2], [3, 4, 1, 2], [3, 4, 2, 1], [4, 1, 2, 3], [4, 3, 1, 2], [4, 3, 2, 1]] !0 = 1 = 1 !1 = 0 = 0 !2 = 1 = 1 !3 = 2 = 2 !4 = 9 = 9 !5 = 44 = 44 !6 = 265 = 265 !7 = 1854 = 1854 !8 = 14833 = 14833 !9 = 133496 = 133496 %2 = 895014631192902121
Perl
Traditional verbose version
<lang Perl>sub d {
# compare this with the deranged() sub to see how to turn procedural
# code into functional one ('functional' as not in 'understandable')
$#_ ? map d([ @{$_[0]}, $_[$_] ], @_[1 .. $_-1, $_+1 .. $#_ ]),
grep { $_[$_] != @{$_[0]} } 1 .. $#_
: $_[0]
}
sub deranged { # same as sub d above, just a readable version to explain method
my ($result, @avail) = @_;
return $result if !@avail; # no more elements to pick from, done
my @list; # list of permutations to return
for my $i (0 .. $#avail) { # try to add each element to result in turn
next if $avail[$i] == @$result; # element n at n-th position, no-no
my $e = splice @avail, $i, 1; # move the n-th element from available to result
push @list, deranged([ @$result, $e ], @avail);
# and recurse down, keep what's returned
splice @avail, $i, 0, $e; # put that element back, try next
}
return @list;
}
sub choose { # choose k among n, i.e. n! / k! (n-k)!
my ($n, $k) = @_;
factorial($n) / factorial($k) / factorial($n - $k)
}
my @fact = (1); sub factorial {
# //= : standard caching technique. If cached value available,
# return it; else compute, cache and return.
# For this specific task not really necessary.
$fact[ $_[0] ] //= $_[0] * factorial($_[0] - 1)
}
my @subfact; sub sub_factorial {
my $n = shift;
$subfact[$n] //= do # same caching stuff, try comment out this line
{
# computes deranged without formula, using recursion
my $total = factorial($n); # total permutations
for my $k (1 .. $n) {
# minus the permutations where k items are fixed
# to original location, and the rest deranged
$total -= choose($n, $k) * sub_factorial($n - $k)
}
$total
}
}
print "Derangements for 4 elements:\n"; my @deranged = d([], 0 .. 3); for (1 .. @deranged) {
print "$_: @{$deranged[$_-1]}\n"
}
print "\nCompare list length and calculated table\n"; for (0 .. 9) {
my @x = d([], 0 .. $_-1);
print $_, "\t", scalar(@x), "\t", sub_factorial($_), "\n"
}
print "\nNumber of derangements:\n"; print "$_:\t", sub_factorial($_), "\n" for 1 .. 20;</lang>
- Output:
Derangements for 4 elements: 1: 1 0 3 2 2: 1 2 3 0 3: 1 3 0 2 4: 2 0 3 1 5: 2 3 0 1 6: 2 3 1 0 7: 3 0 1 2 8: 3 2 0 1 9: 3 2 1 0 Compare list length and calculated table 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 Number of derangements: 1: 0 2: 1 3: 2 4: 9 5: 44 6: 265 7: 1854 8: 14833 9: 133496 10: 1334961 11: 14684570 12: 176214841 13: 2290792932 14: 32071101049 15: 481066515734 16: 7697064251745 17: 130850092279664 18: 2355301661033953 19: 44750731559645106 20: 895014631192902121
Using a module
<lang perl>use ntheory ":all";
- Count derangements using derangement iterator
sub countderange {
my($n,$s) = (shift,0);
forderange { $s++ } $n;
$s;
}
- Count derangements using inclusion-exclusion
sub subfactorial1 {
my $n = shift;
vecsum(map{ vecprod((-1)**($n-$_),binomial($n,$_),factorial($_)) }0..$n);
}
- Count derangements using simple recursion without special functions
sub subfactorial2 {
my $n = shift; use bigint; no warnings 'recursion'; ($n < 1) ? 1 : $n * subfactorial2($n-1) + (-1)**$n;
}
print "Derangements of 4 items:\n"; forderange { print "@_\n" } 4; printf "\n%3s %15s %15s\n","N","List count","!N"; printf "%3d %15d %15d %15d\n",$_,countderange($_),subfactorial1($_),subfactorial2($_) for 0..9; printf "%3d %15s %s\n",$_,"",subfactorial2($_) for 20,200;</lang>
- Output:
Derangements of 4 items: 1 0 3 2 1 2 3 0 1 3 0 2 2 0 3 1 2 3 0 1 2 3 1 0 3 0 1 2 3 2 0 1 3 2 1 0 N List count !N (binomial) !N (recursion) 0 1 1 1 1 0 0 0 2 1 1 1 3 2 2 2 4 9 9 9 5 44 44 44 6 265 265 265 7 1854 1854 1854 8 14833 14833 14833 9 133496 133496 133496 20 895014631192902121 200 290131015521620609254546237518688936375622413566095185632876940298382875066633305125595907908697818551860745708196640009079772455670451355426573609799907339222509103785567575227183775791345718826220455840965346196540544976439608810006794385963854831693077054723298130736781093200499800934036993104223443563872463385599425635345341317933466521378117877578807421014599223577201
Phix
with javascript_semantics function deranged(sequence s1, sequence s2) for i=1 to length(s1) do if s1[i]==s2[i] then return 0 end if end for return 1 end function function derangements(integer n) sequence ts = tagset(n) sequence res = {} for i=1 to factorial(n) do sequence s = permute(i,ts) if deranged(s,ts) then res = append(res,s) end if end for return res end function function subfactorial(integer n) if n<2 then return 1-n end if return (n-1)*(subfactorial(n-1)+subfactorial(n-2)) end function ?derangements(4) for n=0 to 9 do printf(1,"%d: counted:%d, calculated:%d\n",{n,length(derangements(n)),subfactorial(n)}) end for string msg = iff(machine_bits()=32?" (incorrect on 32-bit!)":"") -- (fine on 64-bit) printf(1,"!20=%d%s\n",{subfactorial(20),msg}) include mpfr.e function mpz_sub_factorial(integer n) -- probably not the most efficient way to do this! if n<2 then return sprintf("%d",{1-n}) end if mpz f = mpz_init(mpz_sub_factorial(n-1)), g = mpz_init(mpz_sub_factorial(n-2)) mpz_add(f,f,g) mpz_mul_si(f,f,n-1) string res = mpz_get_str(f) {f,g} = mpz_free({f,g}) return res end function printf(1,"!20=%s (mpfr)\n",{mpz_sub_factorial(20)})
- Output:
{{2,3,4,1},{4,3,1,2},{2,4,1,3},{3,4,2,1},{3,1,4,2},{4,1,2,3},{2,1,4,3},{3,4,1,2},{4,3,2,1}}
0: counted:1, calculated:1
1: counted:0, calculated:0
2: counted:1, calculated:1
3: counted:2, calculated:2
4: counted:9, calculated:9
5: counted:44, calculated:44
6: counted:265, calculated:265
7: counted:1854, calculated:1854
8: counted:14833, calculated:14833
9: counted:133496, calculated:133496
!20=895014631192902186 (incorrect on 32-bit!)
!20=895014631192902121 (mpfr)
(under pwa/p2js you get a trailing "000" instead of "186" for the incorrect result)
A more efficient method of calculating subfactorials (0 should be handled separately, or obviously prepend a 1 and extract with idx+1).
Should you instead of string results want an array of mpz for further calculations, use the mpz_init_set() call as shown:
with javascript_semantics include mpfr.e function subfactorial(integer n) sequence res = repeat(0,n) mpz num = mpz_init(1) for i=1 to n do mpz_mul_si(num,num,i) if mpz_odd(num) then mpz_sub_ui(num,num,1) else mpz_add_ui(num,num,1) end if res[i] = mpz_get_str(num) -- res[i] = mpz_init_set(num) end for return res end function ?extract(subfactorial(20),tagset(9)&20)
- Output:
{"0","1","2","9","44","265","1854","14833","133496","895014631192902121"}
Picat
<lang Picat>import util.
go =>
foreach(N in 0..9)
println([N,num_derangements=num_derangements(N), subfactorial=subfactorial(N), subfactorial2=subfactorial2(N)])
end,
println(["!20", subfactorial(20)]),
println(["!20 approx", subfactorial2(20)]),
println("subfactorial0..30"=[subfactorial(N) : N in 0..30 ]),
println("subfactorial2_0..30"=[subfactorial2(N) : N in 0..30 ]),
println(["!200", subfactorial(200)]),
nl,
println("Syntax sugar:"),
println("'!'(20)"='!'(20)),
println("200.'!'()"=200.'!'()),
println("'!!'(20)"='!!'(20)),
println("'!-!!'(10)"='!-!!'(10)),
nl.
num_derangements(N) = derangements(N).length.
derangements(N) = D =>
D = [P : P in permutations(1..N), nofixpoint(P)].
% subfactorial: tabled recursive function table subfactorial(0) = 1. subfactorial(1) = 0. subfactorial(N) = (N-1)*(subfactorial(N-1)+subfactorial(N-2)).
% approximate version of subfactorial subfactorial2(0) = 1. subfactorial2(N) = floor(1.0*floor(factorial(N)/2.71828 + 1/2.0)).
% Factorial fact(N) = F =>
F1 = 1,
foreach(I in 1..N)
F1 := F1 * I
end,
F = F1.
% No fixpoint in L nofixpoint(L) =>
foreach(I in 1..L.length)
L[I] != I
end.
% Some syntax sugar. Note: the function must be an atom. '!'(N) = fact(N). '!!'(N) = subfactorial(N).
'!-!!'(N) = fact(N) - subfactorial(N).
</lang>
Output:
[0,num_derangements = 1,subfactorial = 1,subfactorial2 = 1] [1,num_derangements = 0,subfactorial = 0,subfactorial2 = 0] [2,num_derangements = 1,subfactorial = 1,subfactorial2 = 1] [3,num_derangements = 2,subfactorial = 2,subfactorial2 = 2] [4,num_derangements = 9,subfactorial = 9,subfactorial2 = 9] [5,num_derangements = 44,subfactorial = 44,subfactorial2 = 44] [6,num_derangements = 265,subfactorial = 265,subfactorial2 = 265] [7,num_derangements = 1854,subfactorial = 1854,subfactorial2 = 1854] [8,num_derangements = 14833,subfactorial = 14833,subfactorial2 = 14833] [9,num_derangements = 133496,subfactorial = 133496,subfactorial2 = 133496] [!20,895014631192902121] [!20 approx,895015233227128960] subfactorial0..30 = [1,0,1,2,9,44,265,1854,14833,133496,1334961,14684570,176214841,2290792932,32071101049,481066515734,7697064251745,130850092279664,2355301661033953,44750731559645106,895014631192902121,18795307255050944540,413496759611120779881,9510425471055777937262,228250211305338670494289,5706255282633466762357224,148362637348470135821287825,4005791208408693667174771274,112162153835443422680893595673,3252702461227859257745914274516,97581073836835777732377428235481] subfactorial2_0..30 = [1,0,1,2,9,44,265,1854,14833,133496,1334962,14684580,176214959,2290794473,32071122622,481066839325,7697069429198,130850180296364,2355303245334550,44750761661356448,895015233227128960,18795319897769705472,413497037750933585920,9510431868271472934912,228250364838515316883456,5706259120962883593175040,148362737145034969127583744,4005793902915943736948031488,112162229281646435629661159424,3252704649167746668444545712128,97581139475032389920237209780224] [!200,290131015521620609254546237518688936375622413566095185632876940298382875066633305125595907908697818551860745708196640009079772455670451355426573609799907339222509103785567575227183775791345718826220455840965346196540544976439608810006794385963854831693077054723298130736781093200499800934036993104223443563872463385599425635345341317933466521378117877578807421014599223577201] Syntax sugar: '!'(20) = 2432902008176640000 200.'!'() = 788657867364790503552363213932185062295135977687173263294742533244359449963403342920304284011984623904177212138919638830257642790242637105061926624952829931113462857270763317237396988943922445621451664240254033291864131227428294853277524242407573903240321257405579568660226031904170324062351700858796178922222789623703897374720000000000000000000000000000000000000000000000000 '!!'(20) = 895014631192902121 '!-!!'(10) = 2293839
PicoLisp
<lang PicoLisp>(load "@lib/simul.l") # For 'permute'
(de derangements (Lst)
(filter
'((L) (not (find = L Lst)))
(permute Lst) ) )
(de subfact (N)
(if (>= 2 N)
(if (= 1 N) 0 1)
(*
(dec N)
(+ (subfact (dec N)) (subfact (- N 2))) ) ) )</lang>
- Output:
: (derangements (range 1 4))
-> ((2 1 4 3) (2 3 4 1) (2 4 1 3) (3 1 4 2) (3 4 1 2) (3 4 2 1) (4 1 2 3) (4 3 1 2) (4 3 2 1))
: (for I (range 0 9)
(tab (2 8 8)
I
(length (derangements (range 1 I)))
(subfact I) ) )
0 1 1
1 0 0
2 1 1
3 2 2
4 9 9
5 44 44
6 265 265
7 1854 1854
8 14833 14833
9 133496 133496
-> NIL
: (subfact 20)
-> 895014631192902121
PureBasic
Brute Force <lang PureBasic> Procedure.q Subfactoral(n) If n=0:ProcedureReturn 1:EndIf If n=1:ProcedureReturn 0:EndIf ProcedureReturn (Subfactoral(n-1)+Subfactoral(n-2))*(n-1) EndProcedure
factFile.s="factorials.txt" tempFile.s="temp.txt" drngFile.s="derangements.txt" DeleteFile(factFile.s) DeleteFile(tempFile.s) DeleteFile(drngFile.s)
n=4
- create our storage file
f.s=factFile.s If CreateFile(0,f.s) WriteStringN(0,"1.2") WriteStringN(0,"2.1") CloseFile(0) Else Debug "not createfile :"+f.s EndIf
showfactorial=#False
If showfactorial
- cw("nfactorial n ="+str(n))
Debug "nfactorial n ="+Str(n) EndIf
- build up the factorial combinations
For l=1 To n-2 Gosub nfactorial Next
- extract the derangements
- cw("derangements["+str(perm(n))+"] for n="+str(n))
Debug "derangements["+Str(Subfactoral(n))+"] for n="+Str(n) Gosub derangements
- cw("")
Debug ""
- show the first 20 derangements
For i=0 To 20 Debug "derangements["+Str(Subfactoral(i))+"] for n="+Str(i) Next
End
derangements: x=0 If ReadFile(0,factFile.s) And CreateFile(1,drngFile.s) Repeat r.s = ReadString(0) cs=CountString(r.s,".") If cs hit=0 t.s=""
- scan for numbers at their index
For i=1 To cs+1 s.s=StringField(r.s,i,".") t.s+s.s+"." If Val(s.s)=i:hit+1:EndIf Next t.s=RTrim(t.s,".")
- show only those which are valid
If Not hit x+1
- cw(t.s+" "+str(x))
Debug t.s+" "+Str(x) WriteStringN(1,t.s+" "+Str(x)) EndIf EndIf Until Eof(0) CloseFile(0) CloseFile(1) Else Debug "not readfile :"+factFile.s Debug "not createfile :"+drngFile.s EndIf
- cw("")
Debug "" Return
nfactorial: x=0 If ReadFile(0,factFile.s) And CreateFile(1,tempFile.s) Repeat r.s = ReadString(0) cs=CountString(r.s,".") If cs For j=1 To cs+2 t.s="" For i=1 To cs+1 s.s=StringField(r.s,i,".") If i=j t.s+"."+Str(cs+2)+"."+s.s Else t.s+"."+s.s EndIf Next If j=cs+2:t.s+"."+Str(cs+2):EndIf t.s=Trim(t.s,".") x+1 If cs+2=n And showfactorial
- cw(t.s+" "+str(x))
Debug t.s+" "+Str(x) EndIf WriteStringN(1,t.s) Next EndIf Until Eof(0) CloseFile(0) CloseFile(1) Else Debug "not readfile :"+factFile.s Debug "not createfile :"+tempFile.s EndIf CopyFile(tempFile.s,factFile.s) DeleteFile(tempFile.s) Return </lang>
- Output:
derangements[9] for n=4 4.3.1.2 1 3.4.1.2 2 3.1.4.2 3 4.1.2.3 4 4.3.2.1 5 3.4.2.1 6 2.3.4.1 7 2.4.1.3 8 2.1.4.3 9 derangements[1] for n=0 derangements[0] for n=1 derangements[1] for n=2 derangements[2] for n=3 derangements[9] for n=4 derangements[44] for n=5 derangements[265] for n=6 derangements[1854] for n=7 derangements[14833] for n=8 derangements[133496] for n=9 derangements[1334961] for n=10 derangements[14684570] for n=11 derangements[176214841] for n=12 derangements[2290792932] for n=13 derangements[32071101049] for n=14 derangements[481066515734] for n=15 derangements[7697064251745] for n=16 derangements[130850092279664] for n=17 derangements[2355301661033953] for n=18 derangements[44750731559645106] for n=19 derangements[895014631192902121] for n=20
<lang PureBasic>Procedure.i deranged(depth, lenn, Array d(1), show)
Protected count, tmp, i
If depth = lenn
If show
For i = 0 To lenn - 1: Print(Chr(d(i) + 'a')): Next
PrintN("")
EndIf
ProcedureReturn 1
EndIf
For i = lenn - 1 To depth Step -1
If i = d(depth): Continue: EndIf
tmp = d(i): d(i) = d(depth): d(depth) = tmp
count + deranged(depth + 1, lenn, d(), show)
tmp = d(i): d(i) = d(depth): d(depth) = tmp
Next
ProcedureReturn count
EndProcedure
Procedure.q sub_fact(n)
If n = 0: ProcedureReturn 1: EndIf If n = 1: ProcedureReturn 0: EndIf ProcedureReturn (sub_fact(n - 1) + sub_fact(n - 2)) * (n - 1)
EndProcedure
Procedure.i gen_n(n, show)
Protected r.i Dim a(1024) For i = 0 To n - 1: a(i) = i: Next ProcedureReturn deranged(0, n, a(), show)
EndProcedure
If OpenConsole()
PrintN("Deranged Four:")
gen_n(4, 1)
PrintN(#CRLF$ + "Compare list vs calc:")
For i = 0 To 9
PrintN(Str(i) + ":" + #TAB$ + Str(gen_n(i, 0)) + #TAB$ + Str(sub_fact(i)))
Next
PrintN(#CRLF$ + "further calc:")
For i = 10 To 20
PrintN(Str(i) + ": " + Str(sub_fact(i)))
Next
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input() CloseConsole()
EndIf</lang>
- Output:
Deranged Four: dabc dcab dcba cdba cdab cadb bdac bcda badc Compare list vs calc: 0: 1 1 1: 0 0 2: 1 1 3: 2 2 4: 9 9 5: 44 44 6: 265 265 7: 1854 1854 8: 14833 14833 9: 133496 133496 further calc: 10: 1334961 11: 14684570 12: 176214841 13: 2290792932 14: 32071101049 15: 481066515734 16: 7697064251745 17: 130850092279664 18: 2355301661033953 19: 44750731559645106 20: 895014631192902121
Python
Includes stretch goal. <lang python>from itertools import permutations import math
def derangements(n):
'All deranged permutations of the integers 0..n-1 inclusive'
return ( perm for perm in permutations(range(n))
if all(indx != p for indx, p in enumerate(perm)) )
def subfact(n):
if n == 2 or n == 0:
return 1
elif n == 1:
return 0
elif 1 <= n <=18:
return round(math.factorial(n) / math.e)
elif n.imag == 0 and n.real == int(n.real) and n > 0:
return (n-1) * ( subfact(n - 1) + subfact(n - 2) )
else:
raise ValueError()
def _iterlen(iter):
'length of an iterator without taking much memory'
l = 0
for x in iter:
l += 1
return l
if __name__ == '__main__':
n = 4
print("Derangements of %s" % (tuple(range(n)),))
for d in derangements(n):
print(" %s" % (d,))
print("\nTable of n vs counted vs calculated derangements")
for n in range(10):
print("%2i %-5i %-5i" %
(n, _iterlen(derangements(n)), subfact(n)))
n = 20
print("\n!%i = %i" % (n, subfact(n)))</lang>
- Output:
Derangements of (0, 1, 2, 3) (1, 0, 3, 2) (1, 2, 3, 0) (1, 3, 0, 2) (2, 0, 3, 1) (2, 3, 0, 1) (2, 3, 1, 0) (3, 0, 1, 2) (3, 2, 0, 1) (3, 2, 1, 0) Table of n vs counted vs calculated derangements 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Quackery
<lang Quackery>
[ stack ] is deranges.num ( --> [ )
forward is (deranges)
[ over size
deranges.num share = iff
[ over temp take
swap nested join
temp put ]
else
[ dup size times
[ 2dup i^ pluck
dip [ over size ]
tuck != iff
[ rot swap
nested join
swap (deranges) ]
else
[ drop 2drop ] ] ]
2drop ] resolves (deranges) ( [ [ --> )
[ dup deranges.num put [] swap times [ i^ join ] [] temp put [] swap (deranges) temp take deranges.num release ] is derangements ( n --> [ )
[ dup 0 = iff [ drop 1 ] done
1 0 rot
1 - times
[ swap over + i^ 1+ * ]
nip ] is sub! ( n --> n )
4 derangements witheach [ echo cr ]
cr
10 times
[ i^ echo sp
i^ derangements size echo sp
i^ sub! echo cr ]
cr
20 sub! echo</lang>
- Output:
[ 1 0 3 2 ] [ 1 2 3 0 ] [ 1 3 0 2 ] [ 2 0 3 1 ] [ 2 3 0 1 ] [ 2 3 1 0 ] [ 3 0 1 2 ] [ 3 2 0 1 ] [ 3 2 1 0 ] 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 895014631192902121
Racket
<lang Racket>
- lang racket
(define (all-misplaced? l)
(for/and ([x (in-list l)] [n (in-naturals 1)]) (not (= x n))))
- 1. Create a named function to generate derangements of the integers 0..n-1.
(define (derangements n)
(define (all-misplaced? l1 l2)
(or (null? l1)
(and (not (eq? (car l1) (car l2)))
(all-misplaced? (cdr l1) (cdr l2)))))
(define l (range n))
(for/list ([p (permutations l)] #:when (all-misplaced? p l))
p))
- 2. Generate and show all the derangements of 4 integers using the above
- routine.
(derangements 4)
- -> '((1 0 3 2) (3 0 1 2) (1 3 0 2) (2 0 3 1) (2 3 0 1)
- (3 2 0 1) (1 2 3 0) (2 3 1 0) (3 2 1 0))
- 3. Create a function that calculates the subfactorial of n, !n.
(define (sub-fact n)
(if (< n 2) (- 1 n)
(* (+ (sub-fact (- n 1)) (sub-fact (- n 2))) (sub1 n))))
- 4. Print and show a table of the counted number of derangements of n vs. the
- calculated !n for n from 0..9 inclusive.
(for ([i 10])
(printf "~a ~a ~a\n" i
(~a #:width 7 #:align 'right (length (derangements i)))
(sub-fact i)))
- Output
- 0 1 1
- 1 0 0
- 2 1 1
- 3 2 2
- 4 9 9
- 5 44 44
- 6 265 265
- 7 1854 1854
- 8 14833 14833
- 9 133496 133496
- Extra
- !20
(sub-fact 20)
- -> 895014631192902121
</lang>
Raku
(formerly Perl 6)
Generate List.permutations and keep the ones where no elements are in their original position. This is done by zipping each permutation with the original list, and keeping the ones where none of the zipped pairs are equal.
I am using the Z infix zip operator with the eqv equivalence infix operator, all wrapped inside a none() Junction.
Although not necessary for this task, I have used eqv instead of == so that the derangements() function also works with any set of arbitrary objects (eg. strings, lists, etc.)
<lang perl6>sub derangements(@l) {
@l.permutations.grep(-> @p { none(@p Zeqv @l) })
}
sub prefix:<!>(Int $n) {
(1, 0, 1, -> $a, $b { ($++ + 2) × ($b + $a) } ... *)[$n]
}
say 'derangements([1, 2, 3, 4])'; say derangements([1, 2, 3, 4]), "\n";
say 'n == !n == derangements(^n).elems'; for 0 .. 9 -> $n {
say "!$n == { !$n } == { derangements(^$n).elems }"
}</lang>
- Output:
derangements([1, 2, 3, 4]) ((2 1 4 3) (2 3 4 1) (2 4 1 3) (3 1 4 2) (3 4 1 2) (3 4 2 1) (4 1 2 3) (4 3 1 2) (4 3 2 1)) n == !n == derangements(^n).elems !0 == 1 == 1 !1 == 0 == 0 !2 == 1 == 1 !3 == 2 == 2 !4 == 9 == 9 !5 == 44 == 44 !6 == 265 == 265 !7 == 1854 == 1854 !8 == 14833 == 14833 !9 == 133496 == 133496
REXX
<lang rexx>/*REXX program generates all permutations of N derangements and subfactorial # */ numeric digits 1000 /*be able to handle large subfactorials*/ parse arg N .; if N== | N=="," then N=4 /*Not specified? Then use the default.*/ d= derangeSet(N) /*go and build the derangements set. */ say d 'derangements for' N "items are:" say
do i=1 for d /*display the derangements for N items.*/
say right('derangement', 22) right(i, length(d) ) '───►' $.i
end /*i*/
say /* [↓] count and calculate subfact !L.*/
do L=0 to 2; d= derangeSet(L)
say L 'items: derangement count='right(d, 6)", !"L'='right( !s(L), 6)
end /*L*/
say say right('!20=' , 22) !s( 20) say right('!200=', 22) !s(200) exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ !s: _=1; do j=1 for arg(1); if j//2 then _= j*_ - 1; else _=j*_ + 1
end /*j*/; return _
/*──────────────────────────────────────────────────────────────────────────────────────*/ derangeSet: procedure expose $.; parse arg x; $.=; #=0; p=x-1
if x==0 then return 1; if x==1 then return 0
@.1=2; @.2=1 /*populate 1st derangement.*/
do i=3 to x; @.i=i; end /*i*/ /* " the rest of 'em.*/
parse value @.p @.x with @.x @.p; call .buildD x /*swap & build.*/
/*build others.*/
do while .nextD(x, 0); call .buildD x; end; return #
/*──────────────────────────────────────────────────────────────────────────────────────*/ .buildD: do j=1 for arg(1); if @.j==j then return; end
#=#+1; do j=1 for arg(1); $.#= $.# @.j; end; return
/*──────────────────────────────────────────────────────────────────────────────────────*/ .nextD: procedure expose @.; parse arg n,i
do k=n-1 by -1 for n-1; kp=k+1; if @.k<@.kp then do; i=k; leave; end
end /*k*/
do j=i+1 while j<n; parse value @.j @.n with @.n @.j; n=n-1
end /*j*/
if i==0 then return 0
do m=i+1 while @.m<@.i; end /*m*/ /* [↓] swap two values. */
parse value @.m @.i with @.i @.m; return 1</lang>
- output when using the default inputs:
9 derangements for 4 items are:
derangement 1 ───► 2 1 4 3
derangement 2 ───► 2 3 4 1
derangement 3 ───► 2 4 1 3
derangement 4 ───► 3 1 4 2
derangement 5 ───► 3 4 1 2
derangement 6 ───► 3 4 2 1
derangement 7 ───► 4 1 2 3
derangement 8 ───► 4 3 1 2
derangement 9 ───► 4 3 2 1
0 items: derangement count= 1, !0= 1
1 items: derangement count= 0, !1= 0
2 items: derangement count= 1, !2= 1
!20= 895014631192902121
!200= 290131015521620609254546237518688936375622413566095185632876940298382875066633305125595907908697818551860745708196640009079772455670451355426573609799907339222509103785567575227183775791345718826220455840965346196540544976439608810006794385963854831693077054723298130736781093200499800934036993104223443563872463385599425635345341317933466521378117877578807421014599223577201
Ruby
<lang ruby>def derangements(n)
ary = (1 .. n).to_a
ary.permutation.select do |perm|
ary.zip(perm).all? {|a,b| a != b}
end
end
def subfact(n)
case n when 0 then 1 when 1 then 0 else (n-1)*(subfact(n-1) + subfact(n-2)) end
end
puts "derangements for n = 4" derangements(4).each{|d|p d}
puts "\n n derange subfact" (0..9).each do |n|
puts "%2d :%8d,%8d" % [n, derangements(n).size, subfact(n)]
end
puts "\nNumber of derangements" (10..20).each do |n|
puts "#{n} : #{subfact(n)}"
end</lang>
- Output:
derangements for n = 4 [2, 1, 4, 3] [2, 3, 4, 1] [2, 4, 1, 3] [3, 1, 4, 2] [3, 4, 1, 2] [3, 4, 2, 1] [4, 1, 2, 3] [4, 3, 1, 2] [4, 3, 2, 1] n derange subfact 0 : 1, 1 1 : 0, 0 2 : 1, 1 3 : 2, 2 4 : 9, 9 5 : 44, 44 6 : 265, 265 7 : 1854, 1854 8 : 14833, 14833 9 : 133496, 133496 Number of derangements 10 : 1334961 11 : 14684570 12 : 176214841 13 : 2290792932 14 : 32071101049 15 : 481066515734 16 : 7697064251745 17 : 130850092279664 18 : 2355301661033953 19 : 44750731559645106 20 : 895014631192902121
Scala
<lang Scala>def derangements(n: Int) =
(1 to n).permutations.filter(_.zipWithIndex.forall{case (a, b) => a - b != 1})
def subfactorial(n: Long): Long = n match {
case 0 => 1 case 1 => 0 case _ => (n - 1) * (subfactorial(n - 1) + subfactorial(n - 2))
}
println(s"Derangements for n = 4") println(derangements(4) mkString "\n")
println("\n%2s%10s%10s".format("n", "derange", "subfact")) (0 to 9).foreach(n => println("%2d%10d%10d".format(n, derangements(n).size, subfactorial(n)))) (10 to 20).foreach(n => println(f"$n%2d${subfactorial(n)}%20d"))</lang>
- Output:
Derangements for n = 4 Vector(2, 1, 4, 3) Vector(2, 3, 4, 1) Vector(2, 4, 1, 3) Vector(3, 1, 4, 2) Vector(3, 4, 1, 2) Vector(3, 4, 2, 1) Vector(4, 1, 2, 3) Vector(4, 3, 1, 2) Vector(4, 3, 2, 1) n derange subfact 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 10 1334961 11 14684570 12 176214841 13 2290792932 14 32071101049 15 481066515734 16 7697064251745 17 130850092279664 18 2355301661033953 19 44750731559645106 20 895014631192902121
SuperCollider
<lang SuperCollider>( d = { |array, n| Routine { n = n ?? { array.size.factorial }; n.do { |i| var permuted = array.permute(i); if(array.every { |each, i| permuted[i] != each }) { permuted.yield }; } }; }; f = { |n| d.((0..n-1)) }; x = f.(4); x.all.do(_.postln); ""; )</lang>
Answers: <lang SuperCollider> [ 3, 2, 1, 0 ] [ 2, 3, 0, 1 ] [ 1, 0, 3, 2 ] [ 1, 2, 3, 0 ] [ 2, 0, 3, 1 ] [ 3, 2, 0, 1 ] [ 1, 3, 0, 2 ] [ 2, 3, 1, 0 ] [ 3, 0, 1, 2 ] </lang>
<lang SuperCollider>( z = { |n| case { n <= 0 } { 1 } { n == 1 } { 0 } { (n - 1) * (z.(n - 1) + z.(n - 2)) } }; p = { |i| i.asPaddedString(10, " ") }; "n derangements subfactorial".postln; (0..9).do { |i| var derangements = f.(i).all; var subfactorial = z.(i); "% % %\n".postf(i, p.(derangements.size), p.(subfactorial)); }; )</lang>
Answers:
<lang SuperCollider> n derangements subfactorial 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 </lang>
Tcl
<lang tcl>package require Tcl 8.5; # for arbitrary-precision integers package require struct::list; # for permutation enumerator
proc derangements lst {
# Special case
if {![llength $lst]} {return {{}}}
set result {}
for {set perm [struct::list firstperm $lst]} {[llength $perm]} \
{set perm [struct::list nextperm $perm]} { set skip 0 foreach a $lst b $perm { if {[set skip [string equal $a $b]]} break } if {!$skip} {lappend result $perm}
} return $result
}
proc deranged1to n {
for {set i 1;set r {}} {$i <= $n} {incr i} {lappend r $i}
return [derangements $r]
}
proc countDeranged1to n {
llength [deranged1to $n]
}
proc subfact n {
if {$n == 0} {return 1}
if {$n == 1} {return 0}
set o 1
set s 0
for {set i 1} {$i < $n} {incr i} {
set s [expr {$i * ($o + [set o $s])}]
} return $s
}</lang> Demonstrating with the display parts of the task: <lang tcl>foreach d [deranged1to 4] {
puts "derangement of 1..4: $d"
}
puts "\n\tcounted\tcalculated" for {set i 0} {$i <= 9} {incr i} {
puts "!$i\t[countDeranged1to $i]\t[subfact $i]"
}
- Stretch goal
puts "\n!20 = [subfact 20]"</lang>
- Output:
derangement of 1..4: 2 1 4 3 derangement of 1..4: 2 3 4 1 derangement of 1..4: 2 4 1 3 derangement of 1..4: 3 1 4 2 derangement of 1..4: 3 4 1 2 derangement of 1..4: 3 4 2 1 derangement of 1..4: 4 1 2 3 derangement of 1..4: 4 3 1 2 derangement of 1..4: 4 3 2 1 counted calculated !0 1 1 !1 0 0 !2 1 1 !3 2 2 !4 9 9 !5 44 44 !6 265 265 !7 1854 1854 !8 14833 14833 !9 133496 133496 !20 = 895014631192902121
Wren
<lang ecmascript>import "/fmt" for Fmt import "/big" for BigInt
var permute // recursive permute = Fn.new { |input|
if (input.count == 1) return [input]
var perms = []
var toInsert = input[0]
for (perm in permute.call(input[1..-1])) {
for (i in 0..perm.count) {
var newPerm = perm.toList
newPerm.insert(i, toInsert)
perms.add(newPerm)
}
}
return perms
}
var derange = Fn.new { |input|
if (input.isEmpty) return [input]
var perms = permute.call(input)
var derangements = []
for (perm in perms) {
var deranged = true
for (i in 0...perm.count) {
if (perm[i] == i) {
deranged = false
break
}
}
if (deranged) derangements.add(perm)
}
return derangements
}
var subFactorial // recursive subFactorial = Fn.new { |n|
if (n == 0) return BigInt.one if (n == 1) return BigInt.zero return (subFactorial.call(n-1) + subFactorial.call(n-2)) * (n - 1)
}
var input = [0, 1, 2, 3] var derangements = derange.call(input) System.print("There are %(derangements.count) derangements of %(input), namely:\n") System.print(derangements.join("\n"))
System.print("\nN Counted Calculated") System.print("- ------- ----------") for (n in 0..9) {
var list = List.filled(n, 0)
for (i in 0...n) list[i] = i
var counted = derange.call(list).count
Fmt.print("$d $-9d $-9i", n, counted, subFactorial.call(n))
} System.print("\n!20 = %(subFactorial.call(20))")</lang>
- Output:
There are 9 derangements of [0, 1, 2, 3], namely: [1, 2, 3, 0] [2, 0, 3, 1] [2, 3, 0, 1] [2, 3, 1, 0] [1, 0, 3, 2] [1, 3, 0, 2] [3, 0, 1, 2] [3, 2, 0, 1] [3, 2, 1, 0] N Counted Calculated - ------- ---------- 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
zkl
mostly
<lang zkl>fcn subFact(n){
if(n==0) return(1); if(n==1) return(0); (n-1)*(self.fcn(n-1) + self.fcn(n-2));
}
fcn derangements(n){
// All deranged permutations of the integers 0..n-1 inclusive
enum:=[0..n-1].pump(List);
Utils.Helpers.permuteW(enum).filter('wrap(perm){
perm.zipWith('==,enum).sum(0) == 0
});
} fcn derangers(n){ // just count # of derangements
enum:=[0..n-1].pump(List);
Utils.Helpers.permuteW(enum).reduce('wrap(sum,perm){
sum + (perm.zipWith('==,enum).sum(0) == 0)
},0);
}</lang> <lang zkl>println("Derangements of 0,1,2,3:\n",derangements(4)); println("\nTable of n vs counted vs calculated derangements:"); foreach n in (10){
println("%2d %-6d %-6d".fmt(n, derangers(n), subFact(n)));
}
n:=20; println("\n!%d = %d".fmt(n, subFact(n)));</lang>
- Output:
Derangements of 0,1,2,3: L(L(3,0,1,2),L(2,0,3,1),L(2,3,0,1),L(3,2,0,1),L(3,2,1,0), L(2,3,1,0),L(1,2,3,0),L(1,3,0,2),L(1,0,3,2)) Table of n vs counted vs calculated derangements: 0 1 1 1 0 0 2 1 1 3 2 2 4 9 9 5 44 44 6 265 265 7 1854 1854 8 14833 14833 9 133496 133496 !20 = 895014631192902121
Lazy/iterators version: <lang zkl>fcn derangements(n){ //-->Walker
enum:=[0..n-1].pump(List);
Utils.Helpers.permuteW(enum).tweak('wrap(perm){
if(perm.zipWith('==,enum).sum(0)) Void.Skip
else perm
});
} fcn derangers(n){ // just count # of derangements, w/o saving them
derangements(n).reduce('+.fpM("10-",1),0); // ignore perm --> '+(1,sum)...
}</lang> <lang zkl>foreach d in (derangements(4)){ println(d) } //rest of test code remains the same</lang>
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