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

总结：

该题主要积累的是矩阵变换的方法，此处主要是两种矩阵的变换，一个是矩阵沿着副对角线变换，另一个是矩阵沿着水平中心线变换。

还有一种方法可以先按照水平中线反转，然后按照主对角线反转。