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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image , which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = [  [1,2,3],  [4,5,6],  [7,8,9]],rotate the input matrix in-place such that it becomes:[  [7,4,1],  [8,5,2],  [9,6,3]]

将2D矩阵顺时针旋转90度。

可以先将矩阵沿对角线做对称变换

[[1, 4, 7],

[2, 5, 8],

[3, 6, 9]]

然后沿水平方向做轴对称即可。

class Solution:    def rotate(self, matrix: List[List[int]]) -> None:        """        Do not return anything, modify matrix in-place instead.        """        n = len(matrix)                for i in range(n):            for j in range(i+1):                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]        for i in range(n):            for j in range(int(n/2)):                matrix[i][j],matrix[i][n-j-1]= matrix[i][n-j-1], matrix[i][j]

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