Rotate Image

Question:

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

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可以先旋转最外围一层,然后依次旋转里层:

 1 class Solution {
 2 public:
 3     void rotate(vector<vector<int>>& matrix) {
 4         int N=matrix.size();
 5     for(int layer=0;layer<N/2;layer++)
 6     {
 7         int first=layer;
 8         int last=N-1-layer;
 9         for(int i=first;i<last;i++)
10         {
11             int offset=i-first;
12             int top=matrix.at(first).at(i);  //save top
13             matrix.at(first).at(i)=matrix.at(last-offset).at(first);  //left->top
14             matrix.at(last-offset).at(first)=matrix.at(last).at(last-offset); //bottom->left
15             matrix.at(last).at(last-offset)=matrix.at(i).at(last);  //right->bottom
16             matrix.at(i).at(last)=top;  //top->right
17         }
18     }
19         
20     }
21 };

 

posted on 2016-04-25 16:12  小菜鸡y  阅读(199)  评论(0编辑  收藏  举报