adventofcode/2023/07/Part2.pm

use 5.38.0;

package Part2;

use Part1;

use List::AllUtils qw/ pairmap sum max /;
use List::UtilsBy  qw/ sort_by /;

sub rank_hand (@hand) {
    @hand = split '', shift @hand if @hand == 1;

    my %group;
    $group{$_}++ for @hand;

    my $jokers = delete $group{'`'} // 0;

    return 7 if 1 >= keys %group;

    return 6 if grep { $_ + $jokers >= 4 } values %group;

    my $max = max values %group;

    if ( $max + $jokers >= 3 ) {
        return 5 if keys %group <= 2;
        return 4;
    }

    return 3 if keys %group == 3;

    return 2 if keys %group == 4;

    return 1;
}

sub handify ($str) {
    state %map = (
        'T' => 10,
        'J' => 1,
        'Q' => 12,
        'K' => 13,
        A   => 14
    );

    my @cards =
      map { chr( ord('a') + $_ - 2 ) } map { $map{$_} // $_ } split '', $str;

    return \@cards;
}

sub parse_input ($input) {
    my @lines      = split "\n", $input;
    my @hand_score = pairmap {
        [ handify($a), $b ]
    }
    map { split " " } @lines;
    return @hand_score;
}

sub score (@hand) {
    join '', rank_hand(@hand), @hand;
}

sub solution_2 ($input) {
    my @hand_score = sort_by { score( $_->[0]->@* ) } parse_input($input);
    my $rank       = 0;
    return sum map { ++$rank * $_->[1] } @hand_score;
}

1;