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])

[download]
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

[download]
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

Replies are listed 'Best First'.
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]

Back to Seekers of Perl Wisdom