75 lines
1.5 KiB
Perl
75 lines
1.5 KiB
Perl
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use 5.36.0;
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use lib '.';
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use DDP;
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use Part1;
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package Part2;
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use Math::Vector::Real;
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use List::AllUtils qw/ uniq /;
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my @directions = map { V(@$_) } [ -1, 0 ], [ 0, 1 ], [ 1, 0 ], [ 0, -1 ];
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sub copy_grid ($grid) {
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return [ map { [@$_] } @$grid ];
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}
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sub add_vectors($x,$y) {
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return [ $x->[0]+$y->[0],$x->[1]+$y->[1]];
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}
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sub do_the_round ($grid) {
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my $guard = Part1::find_guard($grid);
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my $current_direction = 0;
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my %seen;
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my $loop = 0;
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while () {
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my $ahead = $guard + $directions[$current_direction];
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last unless Part1::inside_grid( $grid, $ahead );
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if ( $grid->[ $ahead->[0] ][ $ahead->[1] ] eq '#' ) {
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$current_direction++;
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$current_direction %= @directions;
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redo;
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}
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$guard = $ahead;
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if ( $seen{"$guard"}{$current_direction} ) {
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$loop = 1;
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last;
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}
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$seen{"$guard"}{$current_direction}++;
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}
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return {
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loop => $loop,
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seen => [
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keys %seen
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]
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};
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}
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sub solve ($grid) {
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my $guard = Part1::find_guard($grid);
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my $current_direction = 0;
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my $r = do_the_round($grid);
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my $loops = 0;
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for my $loc ( grep { $grid->[ $_->[0] ][ $_->[1] ] ne '^' }
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map { [/(\d+)/g] } $r->{seen}->@* ) {
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my $copy = copy_grid($grid);
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$copy->[ $loc->[0] ][ $loc->[1] ] = '#';
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$loops++ if do_the_round($copy)->{loop};
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}
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return $loops;
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}
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1;
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