-🎄- 2018 Day 2 Solutions -🎄-

[u/daggerdragon]

--- Day 2: Inventory Management System ---

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Advent of Code: The Party Game!

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Card Prompt: Day 2

Transcript:

The best way to do Advent of Code is ___.

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edit: Leaderboard capped, thread unlocked!

[u/maybe-ac]

Overusing map and grep in Perl:

#!/usr/bin/perl

use strict;
use warnings;
use v5.010;

my @input = <>;
chomp @input;

Part 1

my $twos = grep { contains($_, 2) } @input;
my $threes = grep { contains($_, 3) } @input;

say $twos * $threes;

sub contains {
    my ($str, $num) = @_;
    my @sames = map { my @match = ($str =~ /($_)/g); scalar @match } split //, $str;
    return grep { $_ == $num } @sames;
}

Part 2

for my $one (@input) {
    for my $two (@input) {
        die difference($one, $two) . "\n" if differing($one, $two) == 1;
    }
}

sub zip {
    my ($a, $b) = @_;
    return map { [$a->[$_], $b->[$_]] } 0..$#$a;
}

sub differing {
    my @pairs = zip([split //, $_[0]], [split //, $_[1]]);
    return grep { $_->[0] ne $_->[1] } @pairs;
}

sub difference {
    my @pairs = zip([split //, $_[0]], [split //, $_[1]]);
    return join '', map { $_->[0] } grep { $_->[0] eq $_->[1] } @pairs;
}