ABC problem: Difference between revisions
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>>> can_make_word("CONFUSE")
True
</pre>
=={{header|RPL}}==
Recursion provides an easy way to solve the task. RPL can manage recursive functions, provided that they don't use local variables. All the data must then be managed in the stack, which makes the code somehow difficult to read: one third of the words used by the program are about stack handling: <code>DUP</code>, <code>DROP(N)</code>, <code>PICK</code>, <code>SWAP</code>, <code>ROLL</code> etc.
Recursive search is here systematic: the program does check that ABBA can be written with 2 cubes AB and 2 cubes AC, whatever their order.
{{works with|Halcyon Calc|4.2.7}}
{| class="wikitable"
! RPL code
! Comment
|-
|
≪ SWAP LIST→ → n
≪ n DUP 2 + ROLL - 1 + ROLL n ROLLD
n 1 - →LIST SWAP
≫ ≫ ''''PICKL'''' STO
≪ 1 1 SUB → cubes letter
≪ { } 1 cubes SIZE '''FOR''' j
'''IF''' cubes j GET letter POS
'''THEN''' j + '''END NEXT'''
≫ ≫ ''''GetCubeList'''' STO
≪
DUP2 '''GetCubeList'''
'''IF''' DUP SIZE '''THEN'''
'''IF''' OVER SIZE 1 ==
'''THEN''' 3 DROPN 1
'''ELSE'''
SWAP 2 OVER SIZE SUB
0 SWAP ROT DUP SIZE
'''DO'''
DUP2 GET
6 PICK SWAP '''PICKL''' DROP
4 PICK '''ABC?'''
5 ROLL OR 4 ROLLD
1 -
'''UNTIL''' DUP NOT '''END'''
3 DROPN SWAP DROP
'''END'''
'''ELSE''' 3 DROPN 0 '''END'''
≫ ''''ABC?'''' STO
≪ 1 Words SIZE '''FOR''' w
Words w GET Cubes Words w GET '''ABC?'''
": true" ": false" IFTE + '''NEXT'''
≫ ''''TASK'''' STO
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'''PICKL''' ''( { x1..xm..xn } m -- { x1..xn } xm )''
put selected item at bottom of stack
make a new list with the rest of the stack
'''GetCubeList''' ''( { cubes } "word" -- { match_cubes } )''
Scan cubes
Retain those matching with 1st letter of word
'''ABC?''' ''( { cubes } "word" -- boolean )''
Get the list of cubes matching the 1st letter
if list not empty
if word size = 1 letter
return true
else
initialize stack:
( {cubes} false "ord" { CubeList } index -- )
repeat
get a matching cube index
remove cube from cube list
search cubes for "ord"
update boolean value
back to previous cube index
until all matching cubes checked
clear stack except boolean value
return false if no matching cube
|}
{{in}}
<pre>
{ "BO" "XK" "DQ" "CP" "NA" "GT" "RE" "TG" "QD" "FS" "JW" "HU" "VI" "AN" "OB" "ER" "FS" "LY" "PC" "ZM" } 'Cubes' STO
{ "A" "BARK" "BOOK" "TREAT" "COMMON" "SQUAD" "CONFUSE" } 'Words' STO
TASK
{ "AB" "AB" "AC" "AC" } "ABBA" ABC?
</pre>
{{out}}
<pre>
8: "A: true"
7: "BARK: true"
6: "BOOK: false"
5: TREAT: true"
4: "COMMON: false"
3: "SQUAD: true"
2: "CONFUSE: true"
1: 1
</pre>
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