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?

思路：要求空间复杂度为o(1)，只需发现旋转的规律即可

代码：

void rotate(vector<vector<int> > &matrix) {
     int n=matrix.size();


for(int i=0; i<n-1;++i)
{
for(int j=i; j<n-1-i; ++j)
{
int temp=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]=temp;
}
}   
    }