12.py

from lib import *

input = read_input(2022, 12)


grid = []
start = None
end = None
for i, line in enumerate(input.splitlines()):
    grid.append([ord(c) - 97 if c not in "SE" else {"S": 0, "E": 25}[c] for c in line])
    if "S" in line:
        start = line.index("S"), i
    if "E" in line:
        end = line.index("E"), i
assert start and end


def bfs(start: tuple[int, int], grid, target, step):
    queue: list[tuple[int, int, int]] = [(0, *start)]
    visited = set()
    while queue:
        d, x, y = queue.pop(0)

        if target(x, y):
            return d

        if (x, y) in visited:
            continue
        visited.add((x, y))

        for p, q in get_neighbors(x, y, len(grid[0]), len(grid)):
            if step(x, y, p, q) and (p, q) not in visited:
                queue.append((d + 1, p, q))


print(bfs(start, grid, lambda x, y: (x, y) == end, lambda x, y, p, q: grid[q][p] - grid[y][x] <= 1))
print(bfs(end, grid, lambda x, y: grid[y][x] == 0, lambda x, y, p, q: grid[y][x] - grid[q][p] <= 1))