【Leetcode】Rotate Image

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?

 1 class Solution {
 2 public:
 3     void rotate(vector<vector<int> > &matrix) {
 4         int n = matrix.size();
 5         for(int i = 0; i < n / 2; ++i) { 
 6             for(int j = i; j < n - 1 - i; ++j){  
 7                 int t = matrix[i][j];  
 8                 matrix[i][j] = matrix[n - 1 - j][i];  
 9                 matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];  
10                 matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];  
11                 matrix[j][n - 1 - i] = t;  
12             }  
13         }
14     }
15 };

View Code

由边缘至内部，一圈一圈地旋转。

另外的方法：先将图像沿副对角线翻转，再上下翻转。