Advent of code 2024 day 10 part 2 fast numpy

def day10_part2(s):
  grid = np.array([list(line) for line in s.splitlines()], int)
  grid = np.pad(grid, 1, constant_values=-1)
  a = np.zeros(grid.shape, int)
  a[grid == 0] = 1

  for i in range(1, 10):
    a[1:-1, 1:-1] = a[:-2, 1:-1] + a[2:, 1:-1] + a[1:-1, :-2] + a[1:-1, 2:]
    a[grid != i] = 0

  return a.sum()