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?

这个题倒是比较直接，就是矩阵的旋转。

旋转90°就等价于先上下反转(即关于x轴对称)，再关于原点对称。

#include <iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Solution {
public:
    void rotate(vector<vector<int> > &matrix)
    {
        for(vector<vector<int> >::size_type i=0;i<matrix.size()/2;i++)
            swap(matrix[i],matrix[matrix.size()-i-1]);
        for(int i=1;i<matrix.size();i++)
            for(int j=0;j<i;j++)
            swap(matrix[i][j],matrix[j][i]);
        //cout<<matrix[2][0]<<" "<<matrix[2][1]<<" "<<matrix[2][2]<<endl;
    }
};


int main()
{
    int i1[] = {1,2,3};
    int i2[] = {4,5,6};
    int i3[] = {7,8,9};
    vector<int> mat1(i1,i1+3);
    vector<int> mat2(i2,i2+3);
    vector<int> mat3(i3,i3+3);
    vector<vector<int> > matrix;
    matrix.push_back(mat1);
    matrix.push_back(mat2);
    matrix.push_back(mat3);
    Solution so;
    so.rotate(matrix);
    return 0;
}