permutations of all number in a given set

fadingjava has asked for the wisdom of the Perl Monks concerning the following question:

greetings monks, need help with a very frustrating problem. i have an array of arrays each element of which contains a different number of elements, ranging from 2 to 5.

say @AoA = ([0,1] ,[8,9,10,11])
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now for each of these arrays i want to generate the permutation of all the elements of that array taken 2 at a time. like

0,1
1,0
 
8,9
9,8
8,10
10,8
8,11
11,8
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and so on... cant figure out how to do this? if somebody has written something like this or has any suggestions on possible approach, please help

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Re: permutations of all number in a given set by kvale (Monsignor) on Apr 22, 2004 at 18:17 UTC
Both DamnDirtyApe and Anonymous Monk gave clever, general answers. Here is a simple approach: `my @AoA = ([0,1] ,[8,9,10,11]); foreach my $arr (@AoA) { foreach my $i (0..@$arr-1) { foreach my $j (0..@$arr-1) { next if $i == $j; print "$arr->[$i],$arr->[$j]\n"; } } }` [download] -Mark	[reply] [d/l]
Re: permutations of all number in a given set by DamnDirtyApe (Curate) on Apr 22, 2004 at 17:21 UTC
Take a look at Re: Combinatorics; you could adapt this strategy to your problem. _______________ DamnDirtyApe Those who know that they are profound strive for clarity. Those who would like to seem profound to the crowd strive for obscurity. --Friedrich Nietzsche	[reply]
Re: permutations of all number in a given set by Anomynous Monk (Scribe) on Apr 22, 2004 at 17:50 UTC
`use warnings; use strict; my @aoa = ([1..3],["x".."y"],["a".."c"]); my@perms=map{my$a=$_;map{my$i=$_;map[@$a[$i,$_]],0..$i-1,$i+1..$#$a}0. +.$#$a}@aoa; use Data::Dumper; $Data::Dumper::Indent = 0; print "$_\n" for Dumper @perms; __END__ $VAR1 = [1,2]; $VAR2 = [1,3]; $VAR3 = [2,1]; $VAR4 = [2,3]; $VAR5 = [3,1]; $VAR6 = [3,2]; $VAR7 = ['x','y']; $VAR8 = ['y','x']; $VAR9 = ['a','b']; $VAR10 = ['a','c']; $VAR11 = ['b','a']; $VAR12 = ['b','c']; $VAR13 = ['c','a']; $VAR14 = ['c','b'];` [download]	[reply] [d/l]
Re: permutations of all number in a given set by ysth (Canon) on Apr 22, 2004 at 17:24 UTC
The actual question you ask doesn't seem to have anything to do with your having arrays of arrays; maybe you'd find it easier to think of how to go about it by solving the problem for a simple array and then extending it to your array of arrays.	[reply]


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