print all possible combinations of r elements in a given array of size n

http://www.geeksforgeeks.org/print-all-possible-combinations-of-r-elements-in-a-given-array-of-size-n/

// Program to print all combination of size r in an array of size n

#include<stdio.h>

void combinationUtil(int arr[],int n,int r,int index,int data[],int i);

 

// 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 = new int[r];

 

    // Print all combination using temprary array 'data[]'

    combinationUtil(arr, n, r, 0, data, 0);

}

 

/* arr[]  ---> Input Array

   n      ---> Size of input array

   r      ---> Size of a combination to be printed

   index  ---> Current index in data[]

   data[] ---> Temporary array to store current combination

   i      ---> index of current element in arr[]     */

void combinationUtil(int arr[], int n, int r, int index, int data[], int i)

{

    // Current cobination is ready, print it

    if (index == r)

    {

        for (int j=0; j<r; j++)

            printf("%d ",data[j]);

        printf("\n");

        return;

    }

 

    // When no more elements are there to put in data[]

    if (i >= n)

        return;

 

    // current is included, put next at next location

    data[index] = arr[i];

    combinationUtil(arr, n, r, index+1, data, i+1);

 

    // current is excluded, replace it with next (Note that

    // i+1 is passed, but index is not changed)

    combinationUtil(arr, n, r, index, data, i+1);

}

 

// Driver program to test above functions

int main()

{

    int arr[] = {1, 2, 3, 4, 5};

    int r = 3;

    int n = sizeof(arr)/sizeof(arr[0]);

    printCombination(arr, n, r);

    return 0;

}