55 lines
1.1 KiB
Perl
55 lines
1.1 KiB
Perl
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use 5.38.0;
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package Part2;
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use Part1;
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use List::AllUtils qw/ product sum /;
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sub find_gears($input) {
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my @lines = split "\n", $input;
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unshift @lines, '';
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my @entries;
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for my $i ( 1..$#lines ) {
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my $line = $lines[$i];
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while ( $line =~ /\*/g ) {
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push @entries => {
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prefix => length $`,
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length => length $&,
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line => $i,
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};
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}
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}
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return @entries;
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}
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sub number_near_gear($gear,$number) {
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return if abs( $number->{line} - $gear->{line} ) > 1;
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return ($number->{prefix} <= $gear->{prefix} + 1 and $number->{prefix}+$number->{length} >= $gear->{prefix} );
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}
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sub numbers_near_gear($gear,@numbers) {
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return grep { number_near_gear($gear,$_)} @numbers;
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}
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sub solution_2 ($input) {
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my @numbers = Part1::numbers_near_symbols($input);
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my @gears = find_gears($input);
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my $sum = 0;
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for my $gear ( @gears ) {
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my @near = numbers_near_gear($gear,@numbers);
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next unless @near == 2;
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$sum += product map { $_->{n} } @near;
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}
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return $sum;
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}
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1;
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