Advent of Code 2024 - Historian goes looking for history in all the wrong places

Architeuthis@awful.systems · 16 days ago

Advent of Code 2024 - Historian goes looking for history in all the wrong places

Mii@awful.systems · 15 days ago

Advent of Code is one of these things I wanna do every year and then I end up in fucking end-of-the-year crunch time every December and work for 10-12 hours and really don’t wanna code after work anymore.

But hey, here’s a quick solution for day 1. Let’s see how far I make it.

Day 1

use strict;
use List::Util qw( min max );

open(FH, '<', $ARGV[0]) or die $!;

my @left;
my @right;

while (<FH>) {
	my @nums = split /\s+/, $_;
	push(@left, $nums[0]);
	push(@right, $nums[1]);
}

@left = sort { $b <=> $a } @left;
@right = sort { $b <=> $a } @right;

my $dist = 0;
my $sim = 0;
my $i = 0;

foreach my $lnum (@left) {
	$sim += $lnum * grep { $_ == $lnum } @right;

	my $rnum = $right[$i++];
	$dist += max($lnum, $rnum) - min($lnum, $rnum);
}

print 'Part 1: ', $dist, "\n";
print 'Part 2: ', $sim, "\n";

close(FH);

Mii@awful.systems · 7 days ago

Yay, day 3 with Regexp magic.

Day 3

open(FH, '<', $ARGV[0]) or die $!;
my $sum = 0;
my $sum2 = 0;

my $enabled = 1;

while (<FH>) {
    while ($_ =~ /(?:mul\((\d{1,3}),(\d{1,3})\)|(do)\(\)|(don\'t)\(\))/g) {
        $enabled = 1 if $3;
        $enabled = 0 if $4;
        $sum += $1 * $2 if $1 && $2;
        $sum2 += $1 * $2 if $enabled && $1 && $2;
    }
}

close(FH);

print "Part 1: $sum\n";
print "Part 2: $sum2\n";

Mii@awful.systems · 14 days ago

Day 2, Part 1

use strict;
use List::Util qw( min max );

open(FH, '<', $ARGV[0]) or die $!;
my @lines;
while (<FH>) {
	my @report = split /\s/, $_;
	push @lines, \@report;
}

close FH;

sub in_range {
	my $diff = max($_[0], $_[1]) - min($_[0], $_[1]);
	return $diff >= 1 && $diff <= 3;
}

sub is_safe {
	my $prev = @$_[0];
	my $dir = 0;

	for (my $i = 1; $i < scalar @$_; ++$i) {
		my $el = @$_[$i];
		if ($el > $prev) {
			return 0 unless $dir >= 0;
			$dir = 1;
		} elsif ($el < $prev) {
			return 0 unless $dir <= 0;
			$dir = -1;
		}

		return 0 unless in_range $prev, $el;
		$prev = $el;
	}

	return 1;
}

sub part1 {
	my $safe_reports = 0;

	foreach (@_) {
		$safe_reports++ if is_safe @$_;
	}

	return $safe_reports;
}

print 'Part 1: ', part1(@lines), "\n";

My part 2 solution didn’t work with the real input but worked with all the test cases I threw at it, so I couldn’t figure out what was wrong with it and I’m too lazy to debug any more right now.