Re: random pairs

[jwkrahn]

in reply to random pairs

#!/usr/bin/perl
use warnings;
use strict;

use List::Util 'shuffle';

my @random;
LOOP: {
    @random = shuffle 0 .. 99;
    my %unique;
    for ( 0 .. $#random ) {
        redo LOOP if $_ == $random[ $_ ] || ++$unique{ $_ < $random[ $
+_ ] ? "$_,$random[$_]" : "$random[$_],$_" } > 1;
        }
    }

my @pairs = map [ $_, $random[ $_ ] ], 0 .. $#random;

[CountZero]

You assume that the "predetermined list" is an unbroken sequence of integers from 0 to x. How will you do if it is just a set of integers with duplicates and gaps?