Solution.py

class Solution:
    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
        def add(i1, j1, i2, j2):
            if i1 == i2:
                return [matrix[i1][j] for j in range(j1, j2 + 1)]
            if j1 == j2:
                return [matrix[i][j1] for i in range(i1, i2 + 1)]
            return (
                [matrix[i1][j] for j in range(j1, j2)]
                + [matrix[i][j2] for i in range(i1, i2)]
                + [matrix[i2][j] for j in range(j2, j1, -1)]
                + [matrix[i][j1] for i in range(i2, i1, -1)]
            )

        if not matrix or not matrix[0]:
            return []
        m, n = len(matrix), len(matrix[0])
        i1, j1, i2, j2 = 0, 0, m - 1, n - 1
        res = []
        while i1 <= i2 and j1 <= j2:
            res += add(i1, j1, i2, j2)
            i1, j1, i2, j2 = i1 + 1, j1 + 1, i2 - 1, j2 - 1
        return res