048 - Rotate Image

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?

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Array

 

矩阵旋转的方法：

先左右互换，然后

顺时针则左上右下对角互换，

逆时针则左下右上对角互换。

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

            for(int ii=0; ii<n; ++ii)
                for(int jj=0; jj<(n-ii); ++jj)
                    swap(matrix[ii][jj], matrix[n-1-jj][n-1-ii]);
        }
    }
};

4 ms.