48. Rotate Image

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

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>>& matrix) {
        int n = matrix.size();
        for(int i=0;i<n;++i){
            for(int j=0;j<i;++j){
                swap(matrix[i][j], matrix[j][i]);
            }
        }
        for(int i=0;i<n;++i){
            for(int j=0;j<n/2;++j){
                swap(matrix[i][j], matrix[i][n-1-j]);
            }
        }
    }

};

1. transpose

2. reverse every row