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class Solution:
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    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
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        col, row = len(matrix[0]), len(matrix)
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        l, t, r, b = 0, 0, col - 1, row - 1
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        res = []
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        while l <= r and t <= b:
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            for i in range(l, r):
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                res.append(matrix[t][i])
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            for i in range(t, b):
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                res.append(matrix[i][r])
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            # Append the orphan left by the open interval
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            if t == b:
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                res.append(matrix[t][r])
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            else:
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                # From right to left at the bottom
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                for i in range(r, l, -1):
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                    res.append(matrix[b][i])
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            # Avoid duplicated appending if it is a square
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            if l == r and t != b:
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                res.append(matrix[b][r])
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            else:
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                # From bottom to top at the left
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                for i in range(b, t, -1):
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                    res.append(matrix[i][l])
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            l += 1
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            t += 1
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            r -= 1
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            b -= 1
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        return res