adventofcode2025/day2-1.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 twice
import logging

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

def main():
    with open("day2_input.txt", "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("-")]
        invalids = []
        for k in range(x,y+1):
            s_k = str(k)
            l = len(s_k)
            m = l//2
            if l % 2 == 0:
                if s_k[:m] == s_k[m:]:
                    logger.debug(f"Found a double: {k}")
                    invalids.append(k)
        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()