public static int getCountOfOnes(int n) {
        /*
         Please implement this method to
         return the number of '1's in the binary representation of n
         for any integer n, where n > 0

         Example: for n=6 the binary representation is '110' and the number of '1's in that 
         representation is 2

        */
    	int cnt = 0;
    	String s = Integer.toBinaryString(n);
    	System.out.println("Binary String = " + s);
    	for(int i = 0; i < s.length(); i++){
    		String j = Character.toString(s.charAt(i));

    		if (Character.isDigit(s.charAt(i))){
    			if (j.equalsIgnoreCase("1")) {
    				cnt++;
    			}
    		}
    	}
    	
    	return cnt;
    }

    // Please do not change this interface
    interface ListNode {
        int getItem();
        ListNode getNext();
        void setNext(ListNode next);
    }

    public static ListNode reverse(ListNode node) {
        /*
          Please implement this method to
          reverse a given linked list.
         */
    	ListNode prev = null;
    	ListNode cur = null;
    	ListNode next = null;
    	prev = node;
    	cur = node.getNext();
    	prev.setNext(null);
    	while(cur.getNext()!=null){
    		next = cur.getNext();
    		cur.setNext(prev);
    	}
    	
    	return cur;
    }