Rotate matrix.cpp

// 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]]
// Example 2:


// Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
// Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
// Example 3:

// Input: matrix = [[1]]
// Output: [[1]]
// Example 4:

// Input: matrix = [[1,2],[3,4]]
// Output: [[3,1],[4,2]]
 

// Constraints:

// matrix.length == n
// matrix[i].length == n
// 1 <= n <= 20
// -1000 <= matrix[i][j] <= 1000
//Code:
class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n = matrix.size();
        //taking transverse of matrix
        for(int i=0;i<n;i++){
            for(int j=0;j<i;j++){
                swap(matrix[i][j] , matrix[j][i]);
            }
        }
        // reversing each row in matrix
        for(int i=0;i<n;i++){
            reverse(matrix[i].begin(),matrix[i].end());
        }
    }
};