c++ combination

// C++ program to print all combination  
// of size r in an array of size n  
#include<bits/stdc++.h>  
using namespace std;  
  
void combinationUtil(int arr[], int data[],  
                    int start, int end,  
                    int index, int r);  
  
// The main function that prints  
// all combinations of size r  
// in arr[] of size n. This function 
// mainly uses combinationUtil()  
void printCombination(int arr[], int n, int r)  
{  
    // A temporary array to store 
    // all combination one by one  
    int data[r];  
  
    // Print all combination using 
    // temprary array 'data[]'  
    combinationUtil(arr, data, 0, n-1, 0, r);  
}  
  
/* arr[] ---> Input Array  
data[] ---> Temporary array to  
store current combination  
start & end ---> Staring and 
Ending indexes in arr[]  
index ---> Current index in data[]  
r ---> Size of a combination to be printed */
void combinationUtil(int arr[], int data[],  
                    int start, int end,  
                    int index, int r)  
{  
    // Current combination is ready 
    // to be printed, print it  
    if (index == r)  
    {  
        for (int j = 0; j < r; j++)  
            cout << data[j] << " ";  
        cout << endl;  
        return;  
    }  
  
    // replace index with all possible  
    // elements. The condition "end-i+1 >= r-index" 
    // makes sure that including one element  
    // at index will make a combination with  
    // remaining elements at remaining positions  
    for (int i = start; i <= end &&  
        end - i + 1 >= r - index; i++)  
    {  
        data[index] = arr[i];  
        combinationUtil(arr, data, i+1,  
                        end, index+1, r);  
    }  
}  
  
// Driver code  
int main()  
{  
    int arr[] = {1, 2, 3, 4, 5};  
    int r = 3;  
    int n = sizeof(arr)/sizeof(arr[0]);  
    printCombination(arr, n, r);  
}  
  
// This code is contributed by rathbhupendra