Leetcode: Rotate Image

题目:

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?

 

update

先转置, 后按列翻转

 

class Solution {

public:

    void rotate(vector<vector<int> > &matrix) {

        transpose(matrix);



        for(int i = 0; i < matrix.size(); i ++)

            reverse(matrix[i].begin(), matrix[i].end());



    }



    void transpose(vector<vector<int> > &matrix) {

        int n = matrix.size();



        for(int i = 0; i < n; i ++) {

            for(int j = i; j < n; j ++) {

                swap(matrix[i][j], matrix[j][i]);

            }

        }

    }

};