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;
            }
        }
    }
};