66 lines
1.6 KiB
Perl
66 lines
1.6 KiB
Perl
#!/usr/bin/env perl
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use strict;
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use warnings;
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my @wordgrid = ();
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while (<>) {
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next if /^\s*$/;
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chomp;
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push @wordgrid, [ split //, $_ ];
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}
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my @directions = (
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[[0, 0], [1, 1], [2, 2], [3, 3]],
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[[0, 0], [-1, 1], [-2, 2], [-3, 3]],
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[[0, 0], [0, 1], [0, 2], [0, 3]],
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[[0, 0], [1, 0], [2, 0], [3, 0]],
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[[0, 0], [-1, -1], [-2, -2], [-3, -3]],
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[[0, 0], [1, -1], [2, -2], [3, -3]],
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[[0, 0], [-1, 0], [-2, 0], [-3, 0]],
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[[0, 0], [0, -1], [0, -2], [0, -3]],
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);
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my @diagonal = ([-1, -1], [0, 0], [1, 1]);
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my @otherdiagonal = ([1, -1], [0, 0], [-1, 1]);
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my $xmas_count = 0;
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my $mas_cross_count = 0;
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for my $y (0 .. $#wordgrid) {
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for my $x (0 .. $#{$wordgrid[$y]}) {
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$xmas_count += grep { search_letters([$x, $y], $_, [split //, "XMAS"])} @directions;
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$mas_cross_count++ if search_mas_cross([ $x, $y ]);
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}
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}
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print "Part 1: ", $xmas_count, "\n";
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print "Part 2: ", $mas_cross_count, "\n";
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sub search_letters {
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my ($start, $offsets, $letters) = @_;
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for my $i (0 .. $#{$letters}) {
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my $cord = [$start->[0] + $offsets->[$i]->[0], $start->[1] + $offsets->[$i]->[1]];
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return 0 if (
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$cord->[1] < 0 || $cord->[1] > $#wordgrid ||
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$cord->[0] < 0 || $cord->[0] > $#{$wordgrid[$cord->[1]]}
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);
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return 0 if $wordgrid[$cord->[1]][$cord->[0]] ne $letters->[$i];
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}
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return 1;
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}
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sub search_mas_cross {
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my $start = shift;
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my @mas = split //, "MAS";
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return 0 if $wordgrid[$start->[1]][$start->[0]] ne "A";
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return 0 if (
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!search_letters($start, \@diagonal, \@mas) &&
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!search_letters($start, [reverse @diagonal], \@mas)
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);
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return 0 if (
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!search_letters($start, \@otherdiagonal, \@mas) &&
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!search_letters($start, [reverse @otherdiagonal], \@mas)
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);
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return 1;
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}
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