Map of Highest Peak LeetCode solution in Python

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class Solution:
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    def highestPeak(self, isWater: List[List[int]]) -> List[List[int]]:
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        arr = collections.deque()
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        m, n = len(isWater), len(isWater[0])
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        for i in range(m):
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            for j in range(n):
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                if isWater[i][j] == 1:
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                    arr.append((0, i, j))
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        ans = [[-1] * n for _ in range(m)]
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        while arr:
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            val, x, y = arr.popleft()
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            if ans[x][y] != -1:
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                continue
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            ans[x][y] = val
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            for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
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                xx, yy = x + dx, y + dy
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                if 0 <= xx < m and 0 <= yy < n and ans[xx][yy] == -1:
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                    arr.append((val + 1, xx, yy))
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        return ans