day_17.py

from collections import deque
from hashlib import md5


INPUT = 'bwnlcvfs'
VAULT = 3+3j


def find_vault():
    solutions = []
    que = deque([(0+0j, '')])

    while que:
        pos, path = que.popleft()

        if pos == VAULT:
            solutions.append(path)
            continue

        u, d, l, r = md5((INPUT+path).encode()).hexdigest()[:4]

        if u > 'a' and pos.imag > 0:
            que.append((pos-1j, path+'U'))
        if d > 'a' and pos.imag < 3:
            que.append((pos+1j, path+'D'))
        if l > 'a' and pos.real > 0:
            que.append((pos-1, path+'L'))
        if r > 'a' and pos.real < 3:
            que.append((pos+1, path+'R'))

    return solutions[0], len(solutions[-1])


first, second = find_vault()

print("Let's unlock these doors and find the vault.")
print(f"It's easy, I just need to go like this: {first}.")
print("....")
print("That was too easy, let's spend some more time here.")
print("The longest I was able to walk here and "
      f"still find the vault is {second} steps.")