advent2016_4.py

#!/usr/bin/env python
# http://adventofcode.com/2016
import re
from collections import Counter
import logging as log
import operator

log.basicConfig(level=log.DEBUG, format="%(asctime)s - %(levelname)s - %(message)s")


def partition_string(s):
    # match = re.search(r'(?P<room_string>\.+)(?P<sector_id>[0-9])(?P<checksum>\[[a-z]\])', s)
    room_string = s[:-11].replace("-", "")
    sector_id = s[-10:-7]
    checksum = s[-6:-1]
    return room_string, sector_id, checksum


def is_real_room(room_string, checksum):
    c = Counter(room_string).most_common(100)
    # sort reversed on the value and then by the key
    sorted_c = sorted(c, key=lambda x: (-x[1], x[0]))
    most_common_string = "".join([elem[0] for elem in sorted_c])
    if most_common_string[:5] == checksum:
        return True
    else:
        return False


def caesar_cipher(encrypted_string):
    """from https://inventwithpython.com/chapter14.html"""
    key = int(encrypted_string[-10:-7])
    key = key % 26
    # key = -key
    decrypted = ""
    for symbol in encrypted_string:
        if symbol.isalpha():
            num = ord(symbol)
            num += key
            if symbol.isupper():
                if num > ord("Z"):
                    num -= 26
                elif num < ord("A"):
                    num += 26
            elif symbol.islower():
                if num > ord("z"):
                    num -= 26
                elif num < ord("a"):
                    num += 26

            decrypted += chr(num)
        else:
            decrypted += symbol
    return decrypted[:-11].replace("-", " ")


def sector_sum():
    with open("advent2016-4_input.txt") as file:
        sector_sum = 0
        for line in file:
            line = line.rstrip("\r\n")
            room_string, sector_id, checksum = partition_string(line)
            if is_real_room(room_string, checksum):
                sector_sum += int(sector_id)
    return sector_sum


if __name__ == "__main__":
    with open("advent2016-4_input.txt") as file:
        for line in file:
            line = line.rstrip("\r\n")
            if "north" in caesar_cipher(line):
                print(caesar_cipher(line), line)