StyleInCode

""" day_18_01.py """

# usage: python3 day_18_01.py 70 1024 < input

import sys


def options(loc, space, track, obstacles):
    """ options from loc within space avoiding obstacles but off track """
    output = []
    deltas = [(0, -1), (1, 0), (0, 1), (-1, 0)]
    x0, y0 = loc
    for dx, dy in deltas:
        xd, yd = x0 + dx, y0 + dy
        if all([0 <= xd < space, 0 <= yd < space,
                (xd, yd) not in track, (xd, yd) not in obstacles]):
            output.append((xd, yd))
    return output


size = int(sys.argv[1]) + 1
count = int(sys.argv[2])

with sys.stdin as infile:
    corrupt = {tuple(map(int, row.split(',')))
               for i, row in enumerate(infile) if i < count}

goal = (size - 1, size - 1)
pos = (0, 0)

steps = 0
checked = []
choices = []
while pos != goal:
    ways = options(pos, size, [c for c, _ in choices] + checked, corrupt)
    for w in ways:
        choices.append((w, steps + 1))
    checked.append(pos)
    pos, steps = choices.pop(0)

print(steps)

""" day_18_02.py """

# usage: python3 day_18_02.py 70 < input

import sys


def options(loc, space, track, obstacles):
    """ options from loc within space avoiding obstacles but off track """
    output = []
    deltas = [(0, -1), (1, 0), (0, 1), (-1, 0)]
    x0, y0 = loc
    for dx, dy in deltas:
        xd, yd = x0 + dx, y0 + dy
        if all([0 <= xd < space, 0 <= yd < space,
                (xd, yd) not in track, (xd, yd) not in obstacles]):
            output.append((xd, yd))
    return output


size = int(sys.argv[1]) + 1

with sys.stdin as infile:
    corrupt = [tuple(map(int, row.split(','))) for row in infile]

goal = (size - 1, size - 1)

for i in range(len(corrupt) + 1):
    corrupted = set(corrupt[:i])
    checked = []
    pos = (0, 0)
    choices = [pos]
    while choices:
        pos = choices.pop(0)
        if pos == goal:
            break
        if ways := options(pos, size, choices + checked, corrupted):
            choices.extend(ways)
        checked.append(pos)
    if pos != goal:
        break

print(corrupt[i - 1])