adventofcode/2023/08/Part2.pm

use 5.38.0;

package Part2;

use Part1;

use List::AllUtils qw/all first_index none min max product /;
use List::UtilsBy qw/ min_by max_by /;
    use Math::Utils qw/ lcm /;

sub get_cycle( $current, $directions, $nodes ) {

    my @tracks;
    my $next_index = 0;

    while() {
        my $t = join '-',  $current,$next_index;
        my $i = first_index { $_ eq $t } @tracks;
        if( $i > -1 ) {
            my $c = 0;
            #   p @tracks;
            # warn $i, " ",$t;
            return $i, map {
                $c++;
                if(/Z-/) {
                    my $x = $c; $c = 0; $x;
                }else {
                    ()
                }
            } splice @tracks, $i;
        }
        push @tracks, $t;
        $current = $nodes->{$current}[ $directions->[ $next_index ] ];
        $next_index = ( $next_index+1)% @$directions;
    }


}

sub find_z($current,$next_index,$directions,$nodes) {

    my $visited    = 0;

    while ( ) {
        $visited++;

        $current =
          $nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ];

        last if $current =~ /Z$/ 
    }

    return $visited, $current, $next_index;
}
sub speedrun($current,$next_index,$directions,$nodes,$n) {

        $current =
          $nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ]
            for 1..$n;

    return $current;
}

sub equation_for($current,$directions,$nodes) {

    my $visited = 0;
    my $next_index=0;

    while ( ) {
        $visited++;

        $current =
          $nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ];

        last if $current =~ /Z$/ 
    }

    my $first = $visited;
    $visited = 0;

    while ( ) {
        $visited++;

        $current =
          $nodes->{$current}[ $directions->[ $next_index++ % @$directions ] ];

        last if $current =~ /Z$/ 
    }

    my $entry = {  b => $first, m =>  $visited };
    return $entry;
}


sub solution_2 ($input) {
    my $p          = Part1::parse_input($input);
    my @directions = $p->{directions}->@*;
    my %nodes      = $p->{nodes}->%*;

    my $steps = 0;
    my @paths = grep { /A$/ } keys %nodes;
    my $next_index = 0;

    my @equations = map { equation_for($_,\@directions,\%nodes) } @paths;

    return lcm map { $_->{b} } @equations;

    for(@equations) {
        $_->{i} = 1;
        $_->{total} = $_->{b}+$_->{m};
    }

    until( all { $_->{total} == $equations[0]->{total} } @equations ) {
        my $i = max map { $_->{total} } @equations;

        for(@equations) {
            while( $_->{total}<$i) {
                $_->{total}+=$_->{m};
            }
        }
        #   use DDP; p @equations;
    }

    $equations[0]->{total};
}

1;