498. Diagonal Traverse

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.

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My solution:

public class Solution {    public int[] findDiagonalOrder(int[][] matrix) {        if (matrix == null || matrix.length == 0) return new int[0];        int m = matrix.length;int n = matrix[0].length;int[] re = new int[m * n];boolean flag = true;int mnow = 0;int nnow = 0;for (int i = 0; i < m * n; ++i) {re[i] = matrix[mnow][nnow];if (flag) {if (mnow == 0 || nnow == n - 1) {if (nnow == n - 1)mnow++;elsennow++;flag = false;} else {mnow--;nnow++;}} else {if (mnow == m - 1 || nnow == 0) {if (mnow == m - 1)nnow++;elsemnow++;flag = true;} else {mnow++;nnow--;}}}return re;    }}