59. Spiral Matrix II

 1 class Solution 
 2 {
 3 public:
 4     vector<vector<int>> generateMatrix(int n) 
 5     {
 6         vector<vector<int>> res(n,vector<int> (n,0));
 7         int right=n-1,down=n-1;
 8         int left=0,up=0,k=1;
 9         int lim=n*n;
10         while(k<=lim)
11         {
12             for(int x=left;x<=right;x++)
13                 res[up][x]=k++;
14             up++;
15             for(int y=up;y<=down;y++)
16                 res[y][right]=k++;
17             right--;
18             for(int x=right;x>=left;x--)
19                 res[down][x]=k++;
20             down--;
21             for(int y=down;y>=up;y--)
22                 res[y][left]=k++;
23             left++;
24         }
25         return res;
26     }
27 };