leetcode_c++：Rotate Image（048）

题目

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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算法

复杂度：O(n^2)

1. 对角线swap
2. 行反转

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