1
class Solution {
2
 public:
3
  vector<vector<int>> generateMatrix(int n) {
4
    vector<vector<int>> vec(n, vector<int>(n, 0));
5

6
    vector<int> helper;
7
    for (int i = 0; i < n * n; i++) {
8
      helper.push_back(i + 1);
9
    }
10

11
    int k = 0;
12
    int top = 0;
13
    int down = n - 1;
14

15
    int left = 0;
16
    int right = n - 1;
17

18
    int direction = 0;
19

20
    vector<int> result;
21

22
    while (top <= down and left <= right) {
23
      if (direction == 0) {
24
        for (int i = left; i <= right; i++) {
25
          vec[top][i] = helper[k];
26
          k++;
27
        }
28
        top++;
29
      } else if (direction == 1) {
30
        for (int i = top; i <= down; i++) {
31
          vec[i][right] = helper[k];
32
          k++;
33
        }
34
        right--;
35
      } else if (direction == 2) {
36
        for (int i = right; i >= left; i--) {
37
          vec[down][i] = helper[k];
38
          k++;
39
        }
40
        down--;
41
      } else if (direction == 3) {
42
        for (int i = down; i >= top; i--) {
43
          vec[i][left] = helper[k];
44
          k++;
45
        }
46
        left++;
47
      }
48
      direction = (direction + 1) % 4;
49
    }
50
    return vec;
51
  }
52
};