48. Rotate Image

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

class Solution {
public:
    void rotate(vector<vector<int>>& m) {
        reverse(begin(m), end(m));
        for(int i = 0; i < m.size(); i++)
            for(int j = i + 1; j < m.size(); j++)
                swap(m[i][j],m[j][i]);
    }
};