Rotate Image <leetcode>

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?

思路：首先左右翻转，然后按照左下，右上对角线翻转，代码如下：

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