Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

Example:

Input:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
Output:  [1,2,4,7,5,3,6,8,9]
Explanation:

Note:

1. The total number of elements of the given matrix will not exceed 10,000.

class Solution:
    def findDiagonalOrder(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[int]
        """
        if not matrix or not matrix[0]:
            return []
        res = []
        isRe = 1
        def addLine(row, col, isRe):
            line = []
            while
 
 row < len(matrix) and col >= 0:
                line.append(matrix[row][col])
                row += 1
                col -= 1
            l = len(res)
            if isRe:
                res[l:l] = line[::-1]
            else:
                res[l:l] = line
        for i in range(len(matrix[0])):
            addLine
 
(0, i, isRe)
            isRe ^= 1
        for i in range(1, len(matrix)):
            addLine(i, len(matrix[i]) - 1, isRe)
            isRe ^= 1
        return res

498. Diagonal Traverse 對角線遍歷矩陣