rotate-matrix-90-degree-without-using-extra-space.cpp

// C++ program for left rotation of matrix by 90
// degree wuthout using extra space
#include<bits/stdc++.h>
using namespace std;
#define R 4
#define C 4

// After transpose we swap elements of column
// one by one for finding left rotation of matrix
// by 90 degree
void reverseColumns(int arr[R][C])
{
    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]);
}


// Function for do transpose of matrix
void transpose(int arr[R][C])
{
    for (int i=0; i<R; i++)
        for (int j=i; j<C; j++)
            swap(arr[i][j], arr[j][i]);
}

// Function for print matrix
void printMatrix(int arr[R][C])
{
    for (int i=0; i<R; i++)
    {
        for (int j=0; j<C; j++)
            cout << arr[i][j] << " ";
        cout<<'\n';
    }
}

// Function to anticlockwise rotate matrix
// by 90 degree
void rotate90(int arr[R][C])
{
    transpose(arr);
    reverseColumns(arr);
}

//Driven code
int main()
{
    int arr[R][C]= { {1, 2, 3, 4},
        {5, 6, 7, 8},
        {9, 10, 11, 12},
        {13, 14, 15, 16}
    };
    rotate90(arr);
    printMatrix(arr);
    return 0;
}