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#!/usr/bin/python3
import collections
import functools
Pos = collections.namedtuple('Pos', ['x', 'y'])
def main() -> None:
with open('input', 'r') as f:
grid = tuple(tuple(x.strip()) for x in f.readlines())
pos = Pos(grid[0].index('S'), 0)
print(npaths(grid, pos))
@functools.cache
def npaths(grid: list[list[str]], pos: Pos) -> int:
if pos.y == len(grid):
return 1
if grid[pos.y][pos.x] == '^':
return (
npaths(grid, Pos(pos.x - 1, pos.y))
+ npaths(grid, Pos(pos.x + 1, pos.y))
)
return npaths(grid, Pos(pos.x, pos.y + 1))
if __name__ == '__main__':
main()
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