Leetcode:48. Rotate Image

Description

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?

思路

• 先上下对称交换，然后沿主对角线对称交换

代码

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n = matrix.size();
        if(n <= 1) return;
        
        for(int i = 0; i < n / 2; ++i){
            for(int j = 0; j < n; ++j)
                swap(matrix[i][j], matrix[n - 1 - i][j]);
        }
        
        for(int i = 0; i < n - 1; ++i){
            for(int j = i + 1; j < n; ++j){
                swap(matrix[j][i], matrix[i][j]);
            }
        }
    }
};