[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?

Do not think too much about this problem, don't be scared by the "Matrix" word. This problem can be done in an easy way.
like the picture below:
origin:rotate:

you can read as the 1st picture, and put it on a new one with a different order.

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

this is a naive one, it take extra space to rotate, there are some smarter way which can do in-place transposition. I'll check that later.