Whenever I hear Backtracking in the context of Perl, I think Regular Expressions. So, if you can express the problem as a string, and a matching solution as a regular expression, Perl can solve the problem:

use strict;

my $change = 16;
my @coins = reverse sort qw(2 5);

my $q='1'x$change;

my $solution = join'',map{qr(((?:.{$_})+))} @coins;

$q = ~/^()$solution$/
  or die "Error in regex construction";
{
  # This should maybe be done via @-, but I'm lazy:
  no strict;
  print(length(${$_})/$_, '*', $_) for (1..4)
};

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The key to using Perl effectively is to use its strengths rather than its weaknesses.

Update: Roy Johnson pointed out that I erroneously changed names between testing out and posting - $sol was left over in one place.

In reply to Re: pathsearch/backtracking in Perl - how to solve a problem apparently requiring it? (comparison of Perl with Standard ML) by Corion
in thread pathsearch/backtracking in Perl - how to solve a problem apparently requiring it? (comparison of Perl with Standard ML) by metaperl

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