Longest word made of other words in an array

Write a program to find the longest word made of other words.
Input: test, tester, testertest, testing, testingtester
Output: testingtester


  1. Sort the array according to the length of the string. Longest first.
  2. Starting from the beginning of the resulted array, i.e., the longest string, for each word in the array:
    1. for each of the following word otherWord in the array, processing in order, i.e., from the longest to the shortest
    2. if word contains otherWord, delete otherWord from word and keep searching towards even shorter string.
    3. if at any step word becomes empty, meaning that it can be divided into several shorter words in the array, we should return it since that’s exactly what we wish to find.


	public static class LengthComparator implements Comparator<String> {
		public int compare(String o1, String o2) {
			if (o1.length() < o2.length())
				return 1;
			else if (o1.length() > o2.length())
				return -1;
				return 0;

	public static String longestWordMadeOfOtherWords(String[] words) {
		Arrays.sort(words, new LengthComparator());
		for (String word : words) {
			String backup = new String(word);
			for (String otherWord : words) {
				if (!otherWord.equals(backup) && word.contains(otherWord)) {
					word = word.replace(otherWord, "");
			if (word.length() == 0)
				return backup;
		return null;

1 Comment (+add yours?)

  1. Colin
    May 19, 2013 @ 02:16:20

    Hey, Runhe.
    I think this solution could not fit all cases. I could be wrong.
    Here is my thought.
    If input contains {“abcdefg”, “bcdef”, “bcde”, “fg”, “a”}
    abcdefg will not be found, since it will delete bcdef first.


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