5.pl


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#!/usr/bin/env perl

$ordering_rules = [];
$updates = [];
open($fh, "5-input.txt") or die ;
while (<$fh>) {
  chomp;
  if (m/(\d+)\|(\d+)/) { push @$ordering_rules, [$1, $2]; }
  elsif (m/^\d+,\d+/) { push @$updates, [split(/,/, $_)]; }
}
close($fh);

$sum_no_order = 0;
$sum_order = 0;

for($x=0; $x<scalar @$updates; $x++) {
  if (in_order($ordering_rules, $updates->[$x])) {
    $sum_no_order=$sum_no_order+@{$updates->[$x]}[scalar @{$updates->[$x]} / 2];
  } else {
    @{$updates->[$x]} = sort {
      foreach (@$ordering_rules) {
        if ($_->[0] == $a and $_->[1] == $b) { return -1; }
        elsif ($_->[1] == $a and $_->[0] == $b) { return 1; }
      }
      return 0;
    } @{$updates->[$x]};
    $sum_order=$sum_order+@{$updates->[$x]}[scalar @{$updates->[$x]} / 2];
  }
}

print "puzzle 1: $sum_no_order\n";
print "puzzle 2: $sum_order\n";

sub in_order {
  my ($i, $j) = @_;
  for(my $k=0; $k < scalar @$j; $k++) { return 0 if not in_order_idx($i, $j, $k); }
  return 1;
}

sub in_order_idx {
  my ($i, $j, $k) = @_;
  for (my $x=$k+1; $x<scalar @$j; $x++) {
    for(my $z=0; $z<scalar @$i; $z++) {
      return 0 if @{$i->[$z]}[0] eq $j->[$x] and @{$i->[$z]}[1] eq $j->[$k];
    }
  }

  return 1;
}