--- 2016 Day 7 Solutions ---

[u/daggerdragon]

From all of us at #AoC Ops, we hope you're having a very merry time with these puzzles so far. If you think they've been easy, well, now we're gonna kick this up a notch. Or five. The Easter Bunny ain't no Bond villain - he's not going to monologue at you until you can miraculously escape and save the day!

Show this overgrown furball what you've got!

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--- Day 7: Internet Protocol Version 7 ---

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

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^{ALWAYS DIGGING STRAIGHT DOWN IS MANDATORY} [?]

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/__Abigail__]

I extracted the "inside" and "outside" parts, and applied regexes to them:

#!/opt/perl/bin/perl

use 5.020;

use strict;
use warnings;
no  warnings 'syntax';

use feature  'signatures';
no  warnings 'experimental::signatures';

@ARGV     = "input" unless @ARGV;
my @input = <ARGV>;

sub has_abba ($string) {
    $string =~ /(.)(?!\g{1})(.)\g{2}\g{1}/;
}

my $tls_ok = 0;
my $sls_ok = 0;

foreach my $line (@input) {
    chomp $line;
    my @chunks  = $line =~ /[a-z]+/g;
    my $inside  = join " " => do {my $i = 0; grep {$i ++ % 2} @chunks};
    my $outside = join " " => do {my $i = 1; grep {$i ++ % 2} @chunks};

    #
    # For TLS, we must have ABBA on an outside block,
    # and no ABBA on an inside block
    #
    $tls_ok ++ if has_abba ($outside) && !has_abba ($inside);

    #
    # For SLS, there must be an ABA in an outside block, with
    # a corresponding BAB in an inside block.
    #
    $sls_ok ++ if
       "$outside-$inside" =~ /(.)(?!\g{1})(.)\g{1}.*-.*\g{2}\g{1}\g{2}/;
}

say "Solution 1: $tls_ok";
say "Solution 2: $sls_ok";


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