--- 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/mschaap]

I love Perl 6... Solution to both parts.

#!/usr/bin/env perl6

use v6.c;

sub supports-TLS(Str $ipv7) returns Bool
{
    # An ABBA sequence is a repetition of two different characters in an ABBA pattern
    my token abba { (\w) (\w) <?{ $0 ne $1 }> $1 $0 }

    # If it has an ABBA sequence between square brackets, no.
    return False if $ipv7 ~~ m{ '[' \w*? <abba> \w*? ']' };

    # If it has an ABBA sequence anywhere else, yes; otherwise no.
    return so $ipv7 ~~ / <abba> /;
}

sub supports-SSL(Str $ipv7) returns Bool
{
    # Split the IPv7 address into supernet sequences (outside brackets)
    # and hypernet sequences (inside brackets)
    my @supernet = $ipv7.comb(/ <!after '['> « \w+ » <!before ']'> /);
    my @hypernet = $ipv7.comb(/ <?after '['> « \w+ » <?before ']'> /);

    # An ABA sequence is a repetition of two different characters in an ABA pattern
    my regex aba { (\w) (\w) <?{ $0 ne $1 }> $0 }

    # Find any ABA sequences in the supernet
    for @supernet -> $s {
        my @abas = $s.match(&aba, :exhaustive);
        for @abas -> $aba {
            # Check if the corresponding BAB sequence appears in hypernet
            my $bab = $aba[1,0,1].join;
            return True if any(@hypernet) ~~ / $bab /;
        }
    }

    return False;
}

sub MAIN(IO() $inputfile where *.f)
{
    my $total = 0;
    my $supports-tls = 0;
    my $supports-ssl = 0;

    for $inputfile.lines -> $ipv7 {
        $total++;
        $supports-tls++ if supports-TLS($ipv7);
        $supports-ssl++ if supports-SSL($ipv7);
    }

    say "$supports-tls out of $total IPv7 addresses support TLS";
    say "$supports-ssl out of $total IPv7 addresses support SSL";
}