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feat: add damerau-levenshtein distance algorithm (#6706)
* feat: add damerau-levenshtein distance algorithm * refactor: remove useless parentheses * refactor: add class link to test
This commit is contained in:
Saahil Mahato
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package com.thealgorithms.dynamicprogramming;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import org.junit.jupiter.api.DisplayName;
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import org.junit.jupiter.api.Test;
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/**
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* Unit tests for the {@code DamerauLevenshteinDistance} class.
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* Tests cover edge cases, basic operations, and complex transposition scenarios.
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*/
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class DamerauLevenshteinDistanceTest {
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@Test
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@DisplayName("Should throw exception for null first string")
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void testNullFirstString() {
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assertThrows(IllegalArgumentException.class, () -> { DamerauLevenshteinDistance.distance(null, "test"); });
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}
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@Test
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@DisplayName("Should throw exception for null second string")
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void testNullSecondString() {
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assertThrows(IllegalArgumentException.class, () -> { DamerauLevenshteinDistance.distance("test", null); });
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}
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@Test
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@DisplayName("Should throw exception for both null strings")
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void testBothNullStrings() {
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assertThrows(IllegalArgumentException.class, () -> { DamerauLevenshteinDistance.distance(null, null); });
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}
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@Test
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@DisplayName("Should return 0 for identical strings")
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void testIdenticalStrings() {
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assertEquals(0, DamerauLevenshteinDistance.distance("", ""));
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assertEquals(0, DamerauLevenshteinDistance.distance("a", "a"));
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assertEquals(0, DamerauLevenshteinDistance.distance("abc", "abc"));
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assertEquals(0, DamerauLevenshteinDistance.distance("hello", "hello"));
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}
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@Test
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@DisplayName("Should return length when one string is empty")
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void testEmptyStrings() {
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assertEquals(3, DamerauLevenshteinDistance.distance("", "abc"));
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assertEquals(5, DamerauLevenshteinDistance.distance("hello", ""));
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assertEquals(0, DamerauLevenshteinDistance.distance("", ""));
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}
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@Test
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@DisplayName("Should handle single character insertions")
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void testSingleInsertion() {
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assertEquals(1, DamerauLevenshteinDistance.distance("cat", "cats"));
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assertEquals(1, DamerauLevenshteinDistance.distance("ab", "abc"));
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assertEquals(1, DamerauLevenshteinDistance.distance("", "a"));
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}
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@Test
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@DisplayName("Should handle single character deletions")
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void testSingleDeletion() {
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assertEquals(1, DamerauLevenshteinDistance.distance("cats", "cat"));
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assertEquals(1, DamerauLevenshteinDistance.distance("abc", "ab"));
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assertEquals(1, DamerauLevenshteinDistance.distance("a", ""));
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}
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@Test
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@DisplayName("Should handle single character substitutions")
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void testSingleSubstitution() {
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assertEquals(1, DamerauLevenshteinDistance.distance("cat", "bat"));
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assertEquals(1, DamerauLevenshteinDistance.distance("abc", "adc"));
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assertEquals(1, DamerauLevenshteinDistance.distance("x", "y"));
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}
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@Test
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@DisplayName("Should handle adjacent character transpositions")
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void testAdjacentTransposition() {
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assertEquals(1, DamerauLevenshteinDistance.distance("ab", "ba"));
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assertEquals(1, DamerauLevenshteinDistance.distance("abc", "bac"));
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assertEquals(1, DamerauLevenshteinDistance.distance("hello", "ehllo"));
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}
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@Test
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@DisplayName("Should correctly compute distance for CA to ABC")
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void testCAtoABC() {
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// This is the critical test case that differentiates full DL from OSA
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// Full DL: 2 (insert A at start, insert B in middle)
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// OSA would give: 3
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assertEquals(2, DamerauLevenshteinDistance.distance("CA", "ABC"));
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}
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@Test
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@DisplayName("Should handle non-adjacent transpositions")
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void testNonAdjacentTransposition() {
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assertEquals(2, DamerauLevenshteinDistance.distance("abc", "cba"));
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assertEquals(3, DamerauLevenshteinDistance.distance("abcd", "dcba"));
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}
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@Test
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@DisplayName("Should handle multiple operations")
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void testMultipleOperations() {
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assertEquals(3, DamerauLevenshteinDistance.distance("kitten", "sitting"));
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assertEquals(3, DamerauLevenshteinDistance.distance("saturday", "sunday"));
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assertEquals(5, DamerauLevenshteinDistance.distance("intention", "execution"));
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}
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@Test
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@DisplayName("Should handle completely different strings")
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void testCompletelyDifferentStrings() {
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assertEquals(3, DamerauLevenshteinDistance.distance("abc", "xyz"));
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assertEquals(4, DamerauLevenshteinDistance.distance("hello", "world"));
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}
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@Test
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@DisplayName("Should handle strings with repeated characters")
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void testRepeatedCharacters() {
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assertEquals(0, DamerauLevenshteinDistance.distance("aaa", "aaa"));
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assertEquals(1, DamerauLevenshteinDistance.distance("aaa", "aab"));
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assertEquals(1, DamerauLevenshteinDistance.distance("aaa", "aba"));
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}
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@Test
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@DisplayName("Should be symmetric")
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void testSymmetry() {
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assertEquals(DamerauLevenshteinDistance.distance("abc", "def"), DamerauLevenshteinDistance.distance("def", "abc"));
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assertEquals(DamerauLevenshteinDistance.distance("hello", "world"), DamerauLevenshteinDistance.distance("world", "hello"));
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}
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@Test
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@DisplayName("Should handle case sensitivity")
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void testCaseSensitivity() {
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assertEquals(1, DamerauLevenshteinDistance.distance("Hello", "hello"));
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assertEquals(5, DamerauLevenshteinDistance.distance("HELLO", "hello"));
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}
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@Test
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@DisplayName("Should handle single character strings")
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void testSingleCharacterStrings() {
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assertEquals(1, DamerauLevenshteinDistance.distance("a", "b"));
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assertEquals(0, DamerauLevenshteinDistance.distance("a", "a"));
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assertEquals(2, DamerauLevenshteinDistance.distance("a", "abc"));
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}
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@Test
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@DisplayName("Should handle long strings efficiently")
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void testLongStrings() {
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String s1 = "abcdefghijklmnopqrstuvwxyz";
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String s2 = "abcdefghijklmnopqrstuvwxyz";
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assertEquals(0, DamerauLevenshteinDistance.distance(s1, s2));
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String s3 = "abcdefghijklmnopqrstuvwxyz";
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String s4 = "zyxwvutsrqponmlkjihgfedcba";
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assertEquals(25, DamerauLevenshteinDistance.distance(s3, s4));
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}
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@Test
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@DisplayName("Should satisfy triangle inequality")
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void testTriangleInequality() {
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// d(a,c) <= d(a,b) + d(b,c)
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String a = "cat";
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String b = "hat";
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String c = "rat";
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int ab = DamerauLevenshteinDistance.distance(a, b);
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int bc = DamerauLevenshteinDistance.distance(b, c);
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int ac = DamerauLevenshteinDistance.distance(a, c);
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assertTrue(ac <= ab + bc);
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}
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@Test
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@DisplayName("Should handle special characters")
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void testSpecialCharacters() {
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assertEquals(0, DamerauLevenshteinDistance.distance("hello!", "hello!"));
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assertEquals(1, DamerauLevenshteinDistance.distance("hello!", "hello?"));
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assertEquals(1, DamerauLevenshteinDistance.distance("a@b", "a#b"));
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}
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@Test
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@DisplayName("Should handle numeric strings")
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void testNumericStrings() {
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assertEquals(1, DamerauLevenshteinDistance.distance("123", "124"));
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assertEquals(1, DamerauLevenshteinDistance.distance("123", "213"));
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assertEquals(0, DamerauLevenshteinDistance.distance("999", "999"));
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}
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@Test
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@DisplayName("Should handle unicode characters")
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void testUnicodeCharacters() {
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assertEquals(0, DamerauLevenshteinDistance.distance("café", "café"));
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assertEquals(1, DamerauLevenshteinDistance.distance("café", "cafe"));
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assertEquals(0, DamerauLevenshteinDistance.distance("你好", "你好"));
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}
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}
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