128 lines
2.7 KiB
Perl
128 lines
2.7 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 product /;
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use List::UtilsBy qw/ min_by max_by /;
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use Math::Utils qw/ lcm /;
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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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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 $current;
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}
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sub equation_for($current,$directions,$nodes) {
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my $visited = 0;
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my $next_index=0;
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while ( ) {
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$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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my $first = $visited;
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$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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my $entry = { b => $first, m => $visited };
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return $entry;
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}
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sub solution_2 ($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 $next_index = 0;
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my @equations = map { equation_for($_,\@directions,\%nodes) } @paths;
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return lcm map { $_->{b} } @equations;
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for(@equations) {
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$_->{i} = 1;
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$_->{total} = $_->{b}+$_->{m};
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}
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until( all { $_->{total} == $equations[0]->{total} } @equations ) {
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my $i = max map { $_->{total} } @equations;
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for(@equations) {
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while( $_->{total}<$i) {
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$_->{total}+=$_->{m};
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}
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}
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# use DDP; p @equations;
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}
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$equations[0]->{total};
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}
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1;
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