力扣：498. 对角线遍历

import java.util.Arrays;


public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        // int[][] mat = {{1,2,3},{4,5,6},{7,8,9}};
        // int[][] mat = {{2, 3}};
        int[][] mat = {{3}, {2}};
        System.out.println(Arrays.toString(solution.findDiagonalOrder(mat)));
    }

    
    public int[] findDiagonalOrder(int[][] mat) {
        if (mat.length == 1){
            return mat[0];
        }
        int m = mat.length;
        int n = mat[0].length;
        // 一共有的边
        int edge = m + n - 1;
        int[] ans = new int[m * n];
        int index = 0;

        for (int i = 0; i < edge; i++){
            // 奇数代表从上到下，偶数代表从下到上
            if (i % 2 == 1){
                int x = i < n ? 0 : i - n + 1;
                int y = i < n ? i : n - 1;
                while (x < m && y >= 0){
                    ans[index] = mat[x][y];
                    index++;
                    x++;
                    y--;
                }
            } else {
                int x = i < m ? i : m - 1;
                int y = i < m ? 0 : i - m + 1;
                while (x >= 0 && y < n){
                    ans[index] = mat[x][y];
                    index++;
                    x--;
                    y++;
                }
            }
        }
        return ans;
    }
}