Leetcode -- Spiral Matrix II

class Solution {  
 public:  
   vector<vector<int> > generateMatrix(int n) {  
     vector<vector<int> > result(n, vector<int>(n, 0));  
     int i = 0, j = 0, total = n * n, count = 1;  
     while(count <= total) {  
       for(;j < n && result[i][j] == 0;j++) {  
         result[i][j] = count;  
         count++;  
       }  
       if(count > total) break;  
       j--;  
       i++;  
       for(; i < n && result[i][j] == 0; i++) {  
         result[i][j] = count;  
         count++;  
       }  
       if(count > total) break;  
       i--;  
       j--;  
       for(;j >=0 && result[i][j] == 0; j--) {  
         result[i][j] = count;  
         count++;  
       }  
       if(count > total) break;  
       j++;  
       i--;  
       for(;i >= 0 & result[i][j] == 0; i--) {  
         result[i][j] = count;  
         count++;  
       }  
       if(count > total) break;  
       i++;  
       j++;  
     }  
     return result;  
   }  
 };