【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?

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        int n = matrix.size();
        for(int i = 0; i < n / 2; ++i) { 
            for(int j = i; j < n - 1 - i; ++j){  
                int t = matrix[i][j];  
                matrix[i][j] = matrix[n - 1 - j][i];  
                matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];  
                matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];  
                matrix[j][n - 1 - i] = t;  
            }  
        }
    }
};

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。