89 lines
1.9 KiB
Perl
89 lines
1.9 KiB
Perl
use 5.38.0;
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package Part2;
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use Part1;
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use List::AllUtils qw/all first_index none min max /;
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sub get_cycle( $current, $directions, $nodes ) {
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my @tracks;
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my $next_index = 0;
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while() {
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use DDP; #p @tracks;
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my $t = join '-', $current,$next_index;
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my $i = first_index { $_ eq $t } @tracks;
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if( $i > -1 ) {
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my $c = 0;
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# p @tracks;
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# warn $i, " ",$t;
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return $i, map {
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$c++;
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if(/Z-/) {
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my $x = $c; $c = 0; $x;
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}else {
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()
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}
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} splice @tracks, $i;
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}
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push @tracks, $t;
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$current = $nodes->{$current}[ $directions->[ $next_index ] ];
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$next_index = ( $next_index+1)% @$directions;
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}
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}
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sub find_z($current,$next_index,$directions,$nodes) {
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my $visited = 0;
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while ( ) {
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$visited++;
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$current =
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$nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ];
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last if $current =~ /Z$/
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}
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return $visited, $current, $next_index;
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}
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sub speedrun($current,$next_index,$directions,$nodes,$n) {
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$current =
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$nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ]
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for 1..$n;
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return $current;
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}
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sub solution_2 ($input) {
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my $p = Part1::parse_input($input);
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my @directions = $p->{directions}->@*;
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my %nodes = $p->{nodes}->%*;
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my $steps = 0;
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my @paths = grep { /A$/ } keys %nodes;
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my $next_index = 0;
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until( all {/Z$/ } @paths ) {
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my($incr,$current,$new_index) = find_z($paths[0],$next_index,\@directions,\%nodes);
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$paths[0] = $current;
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@paths = ( $current, map {
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speedrun($paths[$_],$next_index,\@directions,\%nodes,$incr)
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} 1..$#paths );
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$next_index = $new_index;
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$steps += $incr;
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}
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return $steps;
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}
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1;
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