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?

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