/** Calculates the number of permutations for 5 elements */
@Test
public void testPermutations2() {
permutations = new Permutations(5);
permutations.backtracking(0);
int result = permutations.getNumberOfPermutations();
assertEquals(120, result);
}
/** 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;
}
@Test
public void testStringsSameLength() {
assertEquals(Permutations.arePermuations("hellman", "lehlnam"), true);
assertEquals(
Permutations.arePermuations("Lorem Ipsum Dolor Sit Amet", "Ipsum Dolor Amet Sit Lorem"),
true);
}
@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));
}
@Test
public void testDifferentLengthsAreNot() {
assertEquals(Permutations.arePermuations("asd", "asd "), false);
assertEquals(Permutations.arePermuations("asdasdasd", ""), false);
assertEquals(Permutations.arePermuations("wdwdwdw", "wxwxwxw"), false);
}
@Test
public void testSingletons() {
assertEquals(Permutations.arePermuations("a", "b"), false);
assertEquals(Permutations.arePermuations("a", "a"), true);
}
@Test
public void testEmptyStringsArePermutations() {
String arg1 = "";
String arg2 = "";
assertEquals(Permutations.arePermuations(arg1, arg2), true);
}