public static void main(String args[]){
        CombinationOfSizeK kk = new CombinationOfSizeK();
        int arr[] = {1,2,3,4};
        kk.combination(arr, 2);
    }
http://www.geeksforgeeks.org/print-all-possible-combinations-of-r-elements-in-a-given-array-of-size-n/
src/com/interview/recursion/CombinationOfSizeK.java