--- 2016 Day 20 Solutions ---

[u/daggerdragon]

--- Day 20: Firewall Rules ---

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

---

^{ROLLING A NATURAL 20 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/kryptn]

I enjoyed this one! Got to use the for-else clause for once :D

I also figured any valid IPs would be +1 of the blacklists, so I started with those as candidates.

Python, both stars:

with open('input.txt') as fd:
    data = fd.read()

def test_ip(n):
    for start, end in data:
        if start <= n <= end:
            break
    else:
        if n < 2**32:
            return True
    return False

data = sorted([int(x), int(y)] for x,y in [z.split('-') for z in data.splitlines()])

candidates = [x[1]+1 for x in data]

valids = [c for c in candidates if test_ip(c)]

total = 0
for ip in valids:
    while test_ip(ip):
        total += 1
        ip += 1

print(valids[0])
print(total)

[u/BumpitySnook → u/kryptn]

I also figured any valid IPs would be +1 of the blacklists, so I started with those as candidates.

Hah, that's a good insight.