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?

思路：这道题关键在于数组的操作问题上，如何保存中间变量，还有图片的旋转方法。首先将数组分为(行数/2)层，然后一层一层的进行旋转。

class Solution {

public:

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

        if(matrix.size()==0||matrix[0].size()==0)

            return;

        int n=matrix.size();

        int layer=n/2;

        for(int i=0;i<layer;i++)

        {

            for(int j=i;j<n-1-i;j++)

            {

                int temp=matrix[i][j];

                matrix[i][j]=matrix[n-1-j][i];

                matrix[n-1-j][i]=matrix[n-1-i][n-1-j];

                matrix[n-1-i][n-1-j]=matrix[j][n-1-i];

                matrix[j][n-1-i]=temp;

            }

        }

    }

};