private void copyMap(Map<Integer, Integer> t, Map<Integer, Integer> t1) {
		for (Integer i : t.keySet()) {
			int c = t.get(i);
			t1.put(i, c);
		}
	}
-1 in the input means don't use that position

@param k
@param input
@return
src/com/interview/dynamic/PhoneDialNumberOfCombinationOfSizeK.java