adventofcode2024/day05-2.py

import logging

from sys import stdout

# The first section specifies the page ordering rules, one per line. 
# The first rule, 47|53, means that if an update includes both 
# page number 47 and page number 53, then page number 47 must be 
# printed at some point before page number 53. (47 doesn't necessarily 
# need to be immediately before 53; other pages are allowed to be 
# between them.)

# The second section specifies the page numbers of each update. 
# Because most safety manuals are different, the pages needed in the 
# updates are different too. The first update, 75,47,61,53,29, means 
# that the update consists of page numbers 75, 47, 61, 53, and 29.

# For each of the incorrectly-ordered updates, use the page ordering 
# rules to put the page numbers in the right order.
# Find the updates which are not in the correct order. What do you get 
# if you add up the middle page numbers after correctly ordering 
# just those updates?

LOG_FILENAME = "./day04-1.log"
INPUT_FILENAME = "./input04.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 main052():
    with open("./input05.txt", "r", encoding="utf-8") as f:
        lines = [l.strip() for l in f.readlines()]
    
    rules = []
    updates = []
    for i, line in enumerate(lines):
        if "|" not in line:
            first_update = i + 1
            break
        rules.append([int(x) for x in line.split("|")])
    for i, line in enumerate(lines[first_update:]):
        updates.append([int(x) for x in line.split(",")])
    
    valid_updates = []
    invalid_updates = []
    new_invalid_updates = []
    total_vu = 0
    total_iu = 0
    for u in updates:
        relevant_rules = [r for r in rules if all([x in u for x in r])]
        all_valid = all([u.index(rule[0]) < u.index(rule[1]) for rule in relevant_rules])
        if all_valid:
            valid_updates.append(u)
            total_vu += u[(len(u)-1)//2]
        else:
            invalid_updates.append(u)
            logger.info(f"Applying rules to {u}...")
            while not all_valid:
                logger.info(f"{u} still doesn't meet all the rules.")
                for rule in relevant_rules:
                    i1 = u.index(rule[0])
                    i2 = u.index(rule[1])
                    if i1 > i2:
                        u[i1] = rule[1]
                        u[i2] = rule[0]
                        logger.info(f"Swapping {rule[0]} and {rule[1]}, u is now {u}.")
                all_valid = all([u.index(rule[0]) < u.index(rule[1]) for rule in relevant_rules])
            new_invalid_updates.append(u)
            middle_val = u[(len(u)-1)//2]
            logger.info(f"Adding {middle_val} to {total_iu} to get {total_iu + middle_val}.")
            total_iu += middle_val

    print(total_vu)
    logger.info(f"Total of invalid update centers is {total_iu}.")


if __name__ == "__main__":
    main052()