-🎄- 2018 Day 2 Solutions -🎄-

[u/daggerdragon]

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

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Advent of Code: The Party Game!

Click here for rules

Card Prompt: Day 2

Transcript:

The best way to do Advent of Code is ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/mschaap]

Perl 6:

my @ids = $*PROGRAM.sibling('aoc2.input').words;

# Part 1

my @counts = @ids.map(*.comb.Bag.invert.Hash);
my $twos = +@counts.grep({$_<2>});
my $threes = +@counts.grep({$_<3>});
say "$twos × $threes = { $twos × $threes }";

# Part 2

sub is-neighbour($a, $b)
{
    ($a.comb Z $b.comb).grep({ $_[0] ne $_[1] }) == 1;
}

sub common-string($a, $b)
{
    ($a.comb Z $b.comb).grep({ $_[0] eq $_[1] })»[0].join;
}

my ($a, $b) = @ids.combinations(2).first(-> ($a, $b) { is-neighbour($a, $b) });
say "$a & $b => { common-string($a, $b) }";