adventofcode2023/day01-2.py

DEBUG = False
DEBUG_PREFIX = ""

def debug(message, *args, **kwargs):
    if DEBUG:
        print(f"{DEBUG_PREFIX} {message}", *args, **kwargs)

def main():
    from string import digits

    DIGITS_SPELLED = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]

    with open("day01.input", "r") as file:
        input_lines = file.readlines()

    # The calibration value of each line is the first and last digit 
    # in each line, in order, combined to make a two-digit number.
    calibrations = []
    for line in input_lines:
        line = line.strip()
        if line == "":
            continue
        first = ""
        last = ""
        spelled_digits = {}
        first_spelled = len(line) + 1
        last_spelled = -1
        for digit in DIGITS_SPELLED:
            position = 0
            while position < len(line):
                debug(f"{position=}", end=" ")
                if digit in line[position:]:
                    new_index = line[position:].index(digit)
                    spelled_digits[new_index + position] = str(DIGITS_SPELLED.index(digit))
                    position += new_index + 1
                else:
                    position = len(line)
        if len(spelled_digits) > 0:
            first_spelled = min(spelled_digits.keys())
            last_spelled = max(spelled_digits.keys())
        debug(spelled_digits, first_spelled, last_spelled)
        for i, char in enumerate(line):
            if char in digits:
                if i < first_spelled:
                    debug(f"Found first digit in {line} at position {i}: {char}")     
                    first = char
                    break
                else:
                    debug(f"Found first digit in {line} at position {first_spelled}: {spelled_digits[first_spelled]}")
                    first = spelled_digits[first_spelled]
                    break
        for i, char in enumerate(line[::-1]):
            if char in digits:
                if (len(line) - i) > last_spelled:
                    debug(f"Found last digit in {line} at position {len(line) - i}: {char}")
                    last = char
                    break
                else:
                    debug(f"Found last digit in {line} at position {last_spelled}: {spelled_digits[last_spelled]}")
                    last = spelled_digits[last_spelled]
                    break
        calibrations.append(int(first + last))
    
    debug(calibrations)

    # The total calibration value is the sum of the individual
    # calibration values.
    print(f"Total calibration value: {sum(calibrations)}")

if __name__ == "__main__":
    main()