Day 17 - Advent of Code 2016

""" day_17_01_02.py """

# usage: python3 day_17_01_02.py udskfozm

import sys
from hashlib import md5


def status(secret, salt):
    """ what's the door status """
    digest = md5()
    digest.update((secret + salt).encode())
    return [i not in 'bcdef' for i in digest.hexdigest()[:4]]


def move(pos, goal, secret, steps=''):
    """ move to goal """
    global solution

    if pos == goal:
        return pos, steps

    deltas = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    symbols = ['U', 'D', 'L', 'R']

    for i, locked in enumerate(status(secret, steps)):
        if locked:
            continue
        row = pos[0] + deltas[i][0]
        col = pos[1] + deltas[i][1]
        if 0 <= row <= 3 and 0 <= col <= 3:
            next_pos = row, col
            next_steps = steps + symbols[i]
            end_pos, end_steps = move(next_pos, goal, secret, next_steps)
            if end_pos == goal:
                if solution[0] == '' or len(end_steps) < len(solution[0]):
                    solution[0] = end_steps
                if solution[1] == '' or len(end_steps) > len(solution[1]):
                    solution[1] = end_steps

    return pos, steps


passcode = sys.argv[1]
start = 0, 0
end = 3, 3
solution = ['', '']

move(start, end, passcode)
print(solution[0])
print(len(solution[1]))