collections-programming-hard-answers.md

CSE 143

Collections Programming Hard Answers

Final Study Session

1. byAge. One possible solution appears below.

   public static Map<Integer, String> byAge(Map<String, Integer> ages, int min, int max) {
   	Map<Integer, String> result = new TreeMap<Integer, String>();
   	for (String name : ages.keySet()) {
   		int age = ages.get(name);
   		if (min <= age && age <= max) {
   			if (result.containsKey(age)) {
   				result.put(age, result.get(age) + " and " + name);
   			} else {
   				result.put(age, name);
   			}
   		}
   	}
   	return result;
   }

2. extractShorterThan. One possible solution appears below.

   public static Set<String> extractShorterThan2(Set<String> s, int n) {
   	Set<String> result = new TreeSet<String>();
   	Iterator<String> iter = s.iterator();
   	while (iter.hasNext()) {
   		String word = iter.next();
   		if (word.length() < n) {
   			iter.remove();
   			result.add(word);
   		}
   	}
   	return result;
   }