Rotate Image, Rotate Matrix Clock wise. Leetcode, GeeksforGeeks Fast solution

 You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

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:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]

Code

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

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