Rotate Image

LeetCode #48

Description:

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?

Example:

Note

Idea:

先按照行或者列翻转，再transpose。

Code:

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int i=0; 
        int j=matrix.size()-1;
        // 先翻折
        while(i<j){
            swap(matrix[i], matrix[j]);
            i++;
            j--;
        }
        // 再transpose
        for(i=1; i<matrix.size(); ++i){
            for(j=0; j<i; ++j){
                swap(matrix[i][j], matrix[j][i]);
            }
        }

    }
};