54. Spiral Matrix

class Solution:
    def spiralOrder(self, matrix: list[list[int]]) -> list[int]:
        if not matrix or not matrix[0]:
            return []
        M, N = len(matrix), len(matrix[0])
        result = []
        left, right, top, bottom = 0, N - 1, 0, M - 1
        while left <= right and top <= bottom:
            for column in range(left, right + 1):
                result.append(matrix[top][column])
            for row in range(top + 1, bottom + 1):
                result.append(matrix[row][right])
            if left < right and top < bottom:
                for column in range(right - 1, left, -1):
                    result.append(matrix[bottom][column])
                for row in range(bottom, top, -1):
                    result.append(matrix[row][left])
            left, right, top, bottom = left + 1, right - 1, top + 1, bottom - 1
        return result