对角线遍历矩阵

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param mat int整型二维数组
# @return int整型一维数组
#
class Solution:
    def diagonalOrder(self, mat: List[List[int]]) -> List[int]:
        # write code here
        if len(mat) == 0:
            return []
        up_and_right = 1
        x = 0
        y = 0
        res = []
        while not (x == len(mat) - 1 and y == len(mat[0]) - 1):
            res.append(mat[x][y])
            if up_and_right:
                if x - 1 = len(mat[0]):
                    up_and_right = False
                    # 右上部分顺时针寻找
                    if y + 1 < len(mat[0]):
                        y += 1
                        continue
                    if x + 1 < len(mat):
                        x += 1
                        continue
                else:
                    x -= 1
                    y += 1
            else:
                if x + 1 >= len(mat) or y - 1 < 0:
                    up_and_right = True
                    # 左下部分逆时针寻找
                    if x + 1 < len(mat):
                        x += 1
                        continue
                    if y + 1 < len(mat[0]):
                        y += 1
                        continue
                else:
                    x += 1
                    y -= 1
        res.append(mat[x][y])
        return res