adventofcode2025/day2-2.py

# encoding: utf-8

# Given a list of comma-separated pairs of numbers separated by a dash
# e.g. 111-999,22-33
# find all the numbers that are some sequence of digits repeated 
# any number of times

import logging
import random
import re

logger = logging.Logger(__name__)
logger.addHandler(logging.StreamHandler())
logger.setLevel(logging.INFO)

TESTING = False

INPUT_FILE = "day2_test_input.txt" if TESTING else "day2_input.txt"

def main():
    with open(INPUT_FILE, "r") as f:
        input_line = f.readline().strip()
    inranges = [x.strip() for x in input_line.split(",")]
    num_ranges = len(inranges)
    tenths = num_ranges//10
    logger.debug(f"Received {num_ranges} ranges.")
    all_invalids = []
    for i, r in enumerate(inranges):
        if tenths and i % tenths == 0:
            logger.debug(f"Processing range {i}.")
        x, y = [int(q) for q in r.strip().split("-")]
        logger.debug(f"x: {x}, y: {y}")
        invalids = []
        k = x
        while k <= y:
            found = False
            s_k = str(k)
            l = len(s_k)
            m = l//2
            t = 1
            while not found and t <= m:
                pattern = fr'^({s_k[:t]}){{2,}}$'
                found = re.match(pattern, s_k) is not None
                # if random.randint(1,10) == 1:
                logger.debug(f"Pattern: {pattern}, value: {s_k}, found: {found}")
                if found:
                    logger.debug(f"Found a multiple: {k}")
                    invalids.append(k)
                t += 1
            k += 1
        all_invalids.extend(invalids)

    logger.info(f"Found {len(all_invalids)} invalid IDs.")
    logger.info(f"Sum of invalid IDs is {sum(all_invalids)}.")

if __name__ == "__main__":
    main()