1 public List<List<Integer>> printMatrix(int[][] board) {
 2         int height = board.length;
 3         int width = board[0].length;
 4         List<List<Integer>> res = new ArrayList<>();
 5         if (width == 0 || height == 0) {
 6             return res;
 7         }
 8         int diagonal = width + height - 2;
 9         for (int sum = 0; sum <= diagonal; sum++) {
10             List<Integer> cur = new ArrayList<>();
11             for (int y = 0; y <= sum; y++) {
12                 int x = sum - y;
13                 if (y < height && x < width) {
14                     //cur.add(y * width + x + 1);
15                     cur.add(board[y][x]);
16                 }
17             }
18             res.add(cur);
19         }
20         return res;
21     }