Re: random pairs

[BillKSmith]

The second numbers of each pair must be the numbers 0 through 99 in random order. Code this directly.

use List::Util qw( shuffle );

my $n = 0;
my @pairs = map { [$n++, $_] } shuffle( 0..99 );

Update: Sorry guys, I misread the spec.

[CountZero]

I understood that the second element of each pair was to be a random number between 0 and 99. I did not read in the specs that there should be no repeats.

Also it is very well possible that your method yields a combination, the reverse of which is also in the set. Suppose your shuffle yields the list 99 to 0. In that case, every result's reverse is in the set.

[Perlbotics]

Unfortunately, that algorithm does not avoid unwanted pairs like [1,23] and [23,1].

Here is a naive try until it works approach:

use strict;
use warnings;
use List::Util qw(shuffle);

my (%keys, @rnds, @pairs);

do {
  %keys  = ();
  @rnds  = shuffle (0..99);
  @pairs = map{ my $r = $rnds[$_];
                $keys{"$_,$r"}++;
                $keys{"$r,$_"}++;
                [ $_, $r ]
          } (0..99);
} while ( scalar keys %keys != 200 ); # no symmetry means 200 distinct
+ pairs

# @pairs = shuffle( @pairs ); # uncomment if wanted

printf( "%3d %3d\n", @{$pairs[$_]}) for (0..99);