Leetcode 细节实现 Rotate Image

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Rotate Image

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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?

题意：给定一个 n * n 的二维图像，将该图像顺时针旋转 90 度
思路：
先沿副对角线翻转一次，再沿水平中线翻转一次
复杂度：时间O(n^2)，空间O(1)

void rotate(vector<vector<int> > &matrix){int n = matrix.size();//沿副对角线翻转for(int i = 0; i < n; ++i){for(int j = 0; j < n  - i; ++j){int i2 = n - 1 - j, j2 = n - 1 - i;swap(matrix[i][j], matrix[i2][j2]);}}//沿水平中线翻转for(int i = 0; i < n/2; ++i){swap(matrix[i], matrix[n - i - 1]);}}