Question:

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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可以先旋转最外围一层，然后依次旋转里层：

1 class Solution { 2 public: 3     void rotate(vector
     
      
       >& matrix) { 4         int N=matrix.size(); 5     for(int layer=0;layer
       
        top14             matrix.at(last-offset).at(first)=matrix.at(last).at(last-offset); //bottom->left15             matrix.at(last).at(last-offset)=matrix.at(i).at(last);  //right->bottom16             matrix.at(i).at(last)=top;  //top->right17         }18     }19         20     }21 };