32-rotate-by-90-degree.cpp

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

/* matrix : given input matrix, you are require 
 to change it in place without using extra space */
void rotate(vector<vector<int> >& matrix)
{
    int n = matrix.size();
    int k = 1;
    for(int i = 0; i < n; ++i)
    {
        for(int j = k; j < n; ++j)
        {
            int temp = matrix[i][j];
            matrix[i][j] = matrix[j][i];
            matrix[j][i] = temp;
        }
        k++;
    }
    
    for(int i = 0; i < (n / 2); ++i)
    {
        for(int j = 0; j < n; ++j)
        {
            int temp = matrix[i][j];
            matrix[i][j] = matrix[n - i - 1][j];
            matrix[n - i - 1][j] = temp;
        }
    }
}

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;
}

  // } Driver Code Ends