Count Unguarded Cells in the Grid LeetCode solution in Python

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class Solution:
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    def countUnguarded(
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        self, m: int, n: int, guards: List[List[int]], walls: List[List[int]]
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    ) -> int:
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        dp = [[0] * n for _ in range(m)]
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        for x, y in guards + walls:
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            dp[x][y] = 1
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        directions = [(0, 1), (1, 0), (-1, 0), (0, -1)]
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        for x, y in guards:
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            for dx, dy in directions:
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                curr_x = x
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                curr_y = y
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                while (
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                    0 <= curr_x + dx < m
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                    and 0 <= curr_y + dy < n
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                    and dp[curr_x + dx][curr_y + dy] != 1
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                ):
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                    curr_x += dx
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                    curr_y += dy
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                    dp[curr_x][curr_y] = 2
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        return sum(1 for i in range(m) for j in range(n) if dp[i][j] == 0)