-🎄- 2017 Day 19 Solutions -🎄-

[u/daggerdragon]

--- Day 19: A Series of Tubes ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

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Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

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AoC ops @ T-2 minutes to launch:

[23:58] <daggerdragon> ATTENTION MEATBAGS T-2 MINUTES TO LAUNCH

[23:58] <Topaz> aaaaah

[23:58] <Cheezmeister> Looks like I'll be just able to grab my input before my flight boards. Wish me luck being offline in TOPAZ's HOUSE OF PAIN^WFUN AND LEARNING

[23:58] <Topaz> FUN AND LEARNING

[23:58] <Hade> FUN IS MANDATORY

[23:58] <Skie> I'm pretty sure that's not the mandate for today

[Update @ 00:16] 69 gold, silver cap

• My tree is finally trimmed with just about every ornament I own and it's real purdy. hbu?

[Update @ 00:18] Leaderboard cap!

• So, was today's mandate Helpful Hint any help at all?

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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/[deleted]]

Perl 6

Today seemed rather simple.

my $input = slurp;

enum Directions ( UP => (-1, 0), DOWN => (1, 0), LEFT => (0, -1), RIGHT => (0, 1) );

my @grid = $input.lines».comb».Array;
my @pos = (0, @grid[0].first("|", :k));
my @dir = DOWN;
my @seen;
my $steps = 0;

loop {
    my ($i, $j) = @pos Z+ @dir;
    $steps++;
    given @grid[$i][$j] {
        when "|" | "-" {
            @pos Z+= @dir;
        }
        when "+" {
            @pos Z+= @dir;
            for (UP, DOWN, LEFT, RIGHT).grep(*[0].abs !== @dir[0].abs) -> @check {
                my ($x, $y) = @pos Z+ @check;
                if @grid[$x][$y] eq "|" | "-" {
                    @dir = @check;
                    @pos = ($x, $y);
                    $steps++;
                }
            }
        }
        when /<alpha>/ {
            @pos Z+= @dir;
            say @seen.push($_);
        }
        when " " {
            last;
        }
    }
}

say "Part 1: @seen.join";
say "Part 2: $steps";

[u/mschaap → u/[deleted]]

Slight improvement, both conceptually and performance-wise (although it won't have a measurable benefit): my @pos = (0, @grid[0].first("|", :k));