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? http://leetcode.com/onlinejudge#question_48

leetcode_rotate_image.cpp

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        int n = matrix.size();
        for (int leftx = 0; leftx < n / 2; leftx++) {
            int len = n - leftx * 2;
            int rightx = leftx + len - 1;
            for (int i = 0; i < len - 1; ++i) {
                int tmp = matrix[leftx][leftx + i];
                matrix[leftx][leftx + i] = matrix[rightx - i][leftx];
                matrix[rightx - i][leftx] = matrix[rightx][rightx - i];
                matrix[rightx][rightx - i] = matrix[leftx + i][rightx];
                matrix[leftx + i][rightx] = tmp;
            }
        }
    }
};