代码改变世界

leetcode - Spiral Matrix II

2013-10-27 12:11  张汉生  阅读(139)  评论(0)    收藏  举报

 

 1 class Solution {
 2 public:
 3     vector<vector<int> > generateMatrix(int n) {
 4         // Note: The Solution object is instantiated only once and is reused by each test case.
 5         vector<vector<int> > matrix;
 6         if (n<=0)
 7             return matrix;
 8         int flag[4] = {0, n-1, 0, n-1};
 9         int direction = 0; //left 2 right;
10         int i, j;
11         for (i=0; i<n; i++){
12             vector<int> vi;
13             for (j=0; j<n; j++)
14                 vi.push_back(1);
15             matrix.push_back(vi);
16         }
17         int t = 1;
18         while (true){
19             j = 2 - 2 * (direction%2); //j=0 or j=2
20             if (flag[j]>flag[j+1])
21                 break;
22             int start = flag[j]*(1-direction/2) + flag[j+1]*(direction/2); // start of iteration
23             int delta = 1 - direction/2 - direction/2;
24             for (i=start; i<=flag[j+1] && i>=flag[j]; i+=delta){
25                 int rowIndex = i*(direction%2)+ flag[0]*(((direction+3)%4)/3) + flag[1]*(((direction+1)%4)/3);
26                 int colIndex = i*(1-direction%2)+flag[3]*(((direction+2)%4)/3) + flag[2]*(direction/3);
27                 matrix[rowIndex][colIndex]=t++;
28             }
29             int index = 2*(direction%2) + ((direction+1)%4)/2;
30             flag[index] = flag[index] - ((direction+1)%4)/2 + ((direction+3)%4)/2;
31             direction = (direction+1)%4;
32         }
33         return matrix;
34     }
35 };