--- Day 7: Internet Protocol Version 7 ---
While snooping around the local network of EBHQ, you compile a list of IP addresses (they're IPv7, of course; IPv6 is much too limited). You'd like to figure out which IPs support TLS (transport-layer snooping).
An IP supports TLS if it has an Autonomous Bridge Bypass Annotation, or ABBA. An ABBA is any four-character sequence which consists of a pair of two different characters followed by the reverse of that pair, such as xyyx
or abba
. However, the IP also must not have an ABBA within any hypernet sequences, which are contained by square brackets.
For example:
abba[mnop]qrst
supports TLS (abba
outside square brackets).abcd[bddb]xyyx
does not support TLS (bddb
is within square brackets, even thoughxyyx
is outside square brackets).aaaa[qwer]tyui
does not support TLS (aaaa
is invalid; the interior characters must be different).ioxxoj[asdfgh]zxcvbn
supports TLS (oxxo
is outside square brackets, even though it's within a larger string).
How many IPs in your puzzle input support TLS?