#!/usr/local/bin/perl
# day 2015-13

use strict;
use warnings;
use v5.32;
use lib '.';
use Day13 qw( calc_tot_hap_chg );

@ARGV = "input" unless @ARGV;
chomp( my $input = do { local $/; <> } );
my @deltas = split /\n/, $input;
my %people;
my %hap_units;

foreach ( @deltas ) {
    my ( $person, $gain_lose, $units, $neighbor ) =
      m/(\w+) would (gain|lose) (\d+) happiness units by sitting next to (\w+)./;
    $hap_units{$person}{$neighbor} = $gain_lose eq 'gain' ? $units : -1 * $units;
    $people{ $person } += 1;
}

my @people = sort keys %people;

say "part 1: ", calc_tot_hap_chg( \@people, \%hap_units );

foreach my $person ( @people ) {
    $hap_units{ me }{ $person } = 0;
    $hap_units{ $person }{ me } = 0;
}

push @people => 'me';

say "part 2: ", calc_tot_hap_chg( \@people, \%hap_units );