Anonymous user
Permutations/Derangements: Difference between revisions
→{{header|Nim}}
Alextretyak (talk | contribs) m (→{{header|11l}}) |
|||
Line 2,215:
895014631192902121</pre>
=={{header|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>
{{out}}
<pre>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</pre>
=={{header|PARI/GP}}==
| |||