adventofcode2024/day03-2.py

import logging
import re

from functools import reduce
from itertools import pairwise
from sys import stdout

# It seems like the goal of the program is just to multiply some numbers. 
# It does that with instructions like mul(X,Y), where X and Y are each 1-3 
# digit numbers. For instance, mul(44,46) multiplies 44 by 46 to get a 
# result of 2024. Similarly, mul(123,4) would multiply 123 by 4.

# However, because the program's memory has been corrupted, there are also 
# many invalid characters that should be ignored, even if they look like 
# part of a mul instruction. Sequences like mul(4*, mul(6,9!, ?(12,34), or 
# mul ( 2 , 4 ) do nothing.

# For example, consider the following section of corrupted memory:

# xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))

# Adding up the result of each real instruction produces 161 
# (2*4 + 5*5 + 11*8 + 8*5).

# There are two new instructions you'll need to handle:

#     The do() instruction enables future mul instructions.
#     The don't() instruction disables future mul instructions.

# Only the most recent do() or don't() instruction applies. 
# At the beginning of the program, mul instructions are enabled.

LOG_FILENAME = "./day03-1.log"
INPUT_FILENAME = "./input03.txt"

logger = logging.Logger(__name__)
formatter = logging.Formatter('[%(asctime)s][%(levelname)s] %(message)s')
sh = logging.StreamHandler(stdout)
sh.setLevel(logging.INFO)
sh.setFormatter(formatter)
fh = logging.FileHandler(LOG_FILENAME, mode="w", encoding="utf-8")
fh.setLevel(logging.DEBUG)
fh.setFormatter(formatter)
logger.addHandler(sh)
logger.addHandler(fh)

def multiply_pair(s):
    pair = [int(x) for x in s[4:-1].split(",")]
    return reduce(lambda x,y: x*y, pair, 1)

def main():
    with open(INPUT_FILENAME, "r") as f:
        line = "".join(f.readlines())

    MUL_REGEX = r"((do|don't)\(\)|mul\(\d{1,3},\d{1,3}\))"
    matches = re.findall(MUL_REGEX, line)
    ops = [x[0] for x in matches]
    logger.info(ops[:25])
    good_ops = []
    toggle = True
    for o in ops:
        if not toggle and o == "do()":
            toggle = True
            continue
        if toggle:
            if o == "don't()":
                toggle = False
                continue
            if "mul" in o:
                good_ops.append(o)

    total_sum = reduce(lambda x,y: x+y, map(multiply_pair, good_ops))
    logger.info(f"Total sum: {total_sum}")


if __name__ == "__main__":
    main()