# LeetCode-48-Rotate Image-M

xiaoxiao2021-02-28  27

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 in-place, 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] ] Example 2: Given input matrix = [ [ 5, 1, 9,11], [ 2, 4, 8,10], [13, 3, 6, 7], [15,14,12,16] ], rotate the input matrix in-place such that it becomes: [ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11] ]

## 解法一

void rotate(vector<vector<int>>& matrix) { int n=matrix.size(); for(int i=0;i<n/2;i++){ for(int j=i;j<n-i-1;j++){ int z=matrix[i][j]; matrix[i][j]=matrix[n-j-1][i]; matrix[n-j-1][i]=matrix[n-i-1][n-j-1]; matrix[n-i-1][n-j-1]=matrix[j][n-i-1]; matrix[j][n-i-1]=z; } } }

## 解法二

void rotate(vector<vector<int>>& matrix) { int n=matrix.size(); for(int i=0;i<n/2;i++){ for(int j=i;j<n-i-1;j++){ int z=matrix[i][j]; matrix[i][j]=matrix[n-j-1][i]; matrix[n-j-1][i]=matrix[n-i-1][n-j-1]; matrix[n-i-1][n-j-1]=matrix[j][n-i-1]; matrix[j][n-i-1]=z; } } }

## 解法三

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