Ejemplo n.º 1
0
  /** Gets all permutations of a given word. */
  public ArrayList<String> getPermutations() {
    ArrayList<String> result = new ArrayList<String>();

    // The empty string has a single permutation: itself
    if (word.length() == 0) {
      result.add(word);
      return result;
    }

    // Loop through all character positions
    for (int i = 0; i < word.length(); i++) {
      // Form a simpler word by removing the ith character
      String shorterWord = word.substring(0, i) + word.substring(i + 1);

      // Generate all permutations of the simpler word
      Permutations shorterPermutations = new Permutations(shorterWord);
      ArrayList<String> shorterWordPermutations = shorterPermutations.getPermutations();

      // Add the removed character to the front of
      // each permutation of the simpler word,
      for (String s : shorterWordPermutations) {
        result.add(word.charAt(i) + s);
      }
    }
    // Return all permutations
    return result;
  }
Ejemplo n.º 2
0
  @Test
  public void testSimple() throws Exception {
    final String s = "ab";
    final Set<String> expected = new HashSet<>(Arrays.asList("ab", "ba"));

    assertEquals(expected, Permutations.perms(s));
  }