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();
        vector<vector< int>> newm;
        vector< int> v;
         for( int i= 0;i<n;i++)
        {
            v.clear();
             for( int j= 0;j<n;j++)
                v.push_back(matrix[n-j- 1][i]);
            newm.push_back(v);
        }
        matrix= newm;
    }
};