public void combination(int arr[],int k){
        int result[] = new int[k];
        combinationUtil(arr,k,0,result,0);
    }
http://www.geeksforgeeks.org/print-all-possible-combinations-of-r-elements-in-a-given-array-of-size-n/
src/com/interview/recursion/CombinationOfSizeK.java