solution.py

"""
Advent of Code 2022: day 6
"""
import os

from collections import deque


input_file = os.path.join(os.path.dirname(__file__), 'input.txt')
signal = open(input_file).read()


def get_start_marker_index(_signal: str, marker_len: int = 4) -> int:
    """
    Get the index of the start of the signal.
    :param _signal: The received signal.
    :param marker_len: The length of the marker to detect.
    :return: The index of the start of the signal.
    """
    # Set up a history with max length
    history = deque(maxlen=marker_len-1)
    [history.append(None) for _ in range(marker_len-1)]

    # Go over signal to detect start marker
    for i, char in enumerate(_signal):
        # Enough distinct characters, marker encountered
        if all(history) and len({char, *history}) == marker_len:
            return i + 1

        # Oldest are automatically popped due to max deque length
        history.append(char)


solution = get_start_marker_index(signal)
print(f'part1: {solution}')


solution = get_start_marker_index(signal, 14)
print(f'part2: {solution}')