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Combinations and permutations: Difference between revisions

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Combinations and permutations (view source)

Revision as of 07:10, 27 August 2016

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=={{header|REXX}}==
The hard part of this REXX program was coding the   '''DO'''   loops for the various ranges.
<lang rexx>/*REXX program to compute and showdisplays a sampling of combinations and permutations. */
numeric digits 100 /*use 100 decimal digits of precision. */
 
do j=1 for 12; _= /*show all permutations from 1 ──► 12.*/
_=; do k=1 for j /*step through all J permutations. */
_=_ 'P('j","k')='perm(j,k)" " /*add an extra blank between numbers. */
end /*k*/
say strip(_) /*show the permutations horizontally. */
end /*j*/
say /*display a blank line for readability.*/
say
do j=10 to 60 by 10; _= /*show some combinations 10 ──► 60. */
_=; do k= 1 to j by j%5 /*step through some combinations. */
_=_ 'C('j","k')='comb(j,k)" " /*add an extra blank between numbers. */
end /*k*/
say strip(_) /*show the combinations horizontally. */
end /*j*/
say /*display a blank line for readability.*/
say
numeric digits 20 /*force floating point for big numbers.*/
 
do j=5 to 15000 by 1000; _= /*show a few permutations, big numbers.*/
_=; do k=1 to j for 5 by j%10 /*step through some J permutations. */
_=_ 'P('j","k')='perm(j,k)" " /*add an extra blank between numbers. */
end /*k*/
say strip(_) /*show the permutations horizontally. */
end /*j*/
say /*display a blank line for readability.*/
say
do j=100 to 1000 by 100; _= /*show a few combinations, big numbers.*/
_=; do k= 1 to j by j%5 /*step through some combinations. */
_=_ 'C('j","k')='comb(j,k)" " /*add an extra blank between numbers. */
end /*k*/
say strip(_) /*show the combinations horizontally. */
end /*j*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
/*──────────────────────────────────one─liner subroutines─────────────────────*/
perm: procedure; parse arg x,y; call .combPerm; return _
.combPerm: _=1; _=1; do j=x-y+1 to x; _=_*j; end; return _
!: procedure; parse arg x; !=1; do j=2 to x; !=!*j; end; return !
/*──────────────────────────────────────────────────────────────────────────────────────*/
/*────────────────────────────────────────────────────────────────────────────*/
comb: procedure; procedure; parse arg x,y /*arguments: X things, Y at-a-time.*/
if y>x then return 0 if /*oops-say,y too big a>x chunk. then return 0 /*oops-say, an error, too big a chunk.*/
if x=y then return 1 if x =y then return 1 /*X things are the same as chunk size.*/
if x-y<y then y=x-y if x-y <y then y=x - y /*switch things around for speed. */
call .combPerm call .combPerm /*call subroutine to do heavy lifting. */
return _/!(y) return _ / !(y) /*just perform one last division. */</lang>
'''output'''
<pre>
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