Do not forget to assign size value of matrix. This is very important!!!!

1 class Solution { 2 public: 3     vector
     
      
        > generateMatrix(int n) { 4         vector
       
        
          > result(n, vector
         
          (n, 0)); 5         int count = 1; 6         for (int i = 0; i < n/2; i++) { 7             for (int j = i; j < n-i-1; j++) result[i][j] = count++; 8             for (int j = i; j < n-i-1; j++) result[j][n-i-1] = count++; 9             for (int j = n-i-1; j > i; j--) result[n-i-1][j] = count++;10             for (int j = n-i-1; j > i; j--) result[j][i] = count++;11         }12         if (n%2 == 1) result[n/2][n/2] = count;13         return result;14     }15 };