Leetcode Rotate Image

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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?

矩陣的旋轉

如

1 2 3

4 5 6

7 8 9

順時針旋轉90度為

7 4 1

8 5 2

9 6 3

（i,j）旋轉後變成 (j,n-i-1)

class Solution {public:    void rotate(vector<vector<int> > &matrix) {        int n = matrix.size();        for(int i = 0 ;i  < n/2; ++ i){            for(int j = i; j < n - i-1; ++ j){                swap(matrix[i][j],matrix[j][n-i-1]);                 swap(matrix[i][j],matrix[n-i-1][n-j-1]);                swap(matrix[i][j],matrix[n-j-1][i]);            }        }    }};