Rotate_matrix_by_90_degrees.cpp

#include<bits/stdc++.h>
using namespace std;
void rotate (vector<vector<int> >& matrix);

// Given a square matrix[][] of size N x N. 
// The task is to rotate it by 90 degrees in an anti-clockwise direction without using any extra space
 
 
    void revcol(vector<vector<int> >& arr)
    {
        int R = arr.size();
        int C = arr[0].size();
        for (int i = 0; i < C; i++)
            for (int j = 0, k = C - 1;
                 j < k; j++, k--)
                swap(arr[j][i], arr[k][i]);
    }

     void transpose(vector<vector<int> >& arr)
        {
            int R = arr.size();
            int C = arr[0].size();
            for (int i = 0; i < R; i++)
                for (int j = i; j < C; j++)
                    swap(arr[i][j], arr[j][i]);
        }
 
        void rotate(vector<vector<int> >& matrix)
        {
            transpose(matrix);
            revcol(matrix);
           
        }




int main()
{
    int t;
    cin>>t; 
    while(t--)
    {
        int n;
        cin>>n; 
        vector<vector<int> > matrix(n);
        for(int i=0; i<n; i++)
        {
            matrix[i].resize(n);
            for(int j=0; j<n; j++)
                cin>>matrix[i][j]; 
        }
        rotate(matrix);
        for (int i = 0; i < n; ++i)
        {
            for(int j=0; j<n; j++)
                cout<<matrix[i][j]<<" ";
            cout<<"\n";
        }
    }
    return 0;
}