【leetcode刷题】20T23-螺旋矩阵

示例 1:
输入:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
输出: [1,2,3,6,9,8,7,4,5]

示例 2:
输入:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

class Solution(object):
    def spiralOrder(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[int]
        """
        if len(matrix) == 0 or len(matrix[0]) == 0:
            return []
        up, down = 0, len(matrix) - 1
        left, right = 0, len(matrix[0]) - 1
        res = []
        i, j = 0, 0

        while up <= i <= down and left <= j <= right:
            # 上方一行
            for j in range(left, right + 1):
                res.append(matrix[i][j])
            up += 1
            if up > down:
                break
            # 右方一列
            j = right
            for i in range(up, down + 1):
                res.append(matrix[i][j])
            right -= 1
            if left > right:
                break
            # 下方一行
            i = down
            for j in range(right, left - 1, -1):
                res.append(matrix[i][j])
            down -= 1
            if up > down:
                break
            # 左方一列
            j = left
            for i in range(down, up - 1, -1):
                res.append(matrix[i][j])
            left += 1
            if left > right:
                break
            i = up
            j = left
        return res