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feat(compression): Add Burrows-Wheeler Transform (BWT) and Move-to-Front (MTF) (#6926)
* feat(compression): Add Burrows-Wheeler Transform (BWT) and Move-to-Front (MTF) * Resolve SpotBugs * fix code style
This commit is contained in:
Indolyn Yi
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package com.thealgorithms.compression;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNotEquals;
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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.Test;
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public class BurrowsWheelerTransformTest {
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@Test
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public void testTransformAndInverseBanana() {
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String original = "banana$";
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BurrowsWheelerTransform.BWTResult expectedTransform = new BurrowsWheelerTransform.BWTResult("annb$aa", 4);
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// Test forward transform
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BurrowsWheelerTransform.BWTResult actualTransform = BurrowsWheelerTransform.transform(original);
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assertEquals(expectedTransform, actualTransform);
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// Test inverse transform
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String reconstructed = BurrowsWheelerTransform.inverseTransform(actualTransform.transformed, actualTransform.originalIndex);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testTransformAndInverseAbracadabra() {
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String original = "abracadabra$";
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BurrowsWheelerTransform.BWTResult expectedTransform = new BurrowsWheelerTransform.BWTResult("ard$rcaaaabb", 3);
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// Test forward transform
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BurrowsWheelerTransform.BWTResult actualTransform = BurrowsWheelerTransform.transform(original);
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assertEquals(expectedTransform, actualTransform);
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// Test inverse transform
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String reconstructed = BurrowsWheelerTransform.inverseTransform(actualTransform.transformed, actualTransform.originalIndex);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testTransformAndInverseSixMixPixFix() {
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String original = "SIX.MIX.PIX.FIX$";
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BurrowsWheelerTransform.BWTResult expectedTransform = new BurrowsWheelerTransform.BWTResult("XXXX.FPSM..$IIII", 11);
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// Test forward transform
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BurrowsWheelerTransform.BWTResult actualTransform = BurrowsWheelerTransform.transform(original);
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assertEquals(expectedTransform, actualTransform);
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// Test inverse transform
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String reconstructed = BurrowsWheelerTransform.inverseTransform(actualTransform.transformed, actualTransform.originalIndex);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testEmptyString() {
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String original = "";
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BurrowsWheelerTransform.BWTResult expectedTransform = new BurrowsWheelerTransform.BWTResult("", -1);
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BurrowsWheelerTransform.BWTResult actualTransform = BurrowsWheelerTransform.transform(original);
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assertEquals(expectedTransform, actualTransform);
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String reconstructed = BurrowsWheelerTransform.inverseTransform(actualTransform.transformed, actualTransform.originalIndex);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testSingleCharacter() {
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String original = "a";
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BurrowsWheelerTransform.BWTResult expectedTransform = new BurrowsWheelerTransform.BWTResult("a", 0);
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BurrowsWheelerTransform.BWTResult actualTransform = BurrowsWheelerTransform.transform(original);
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assertEquals(expectedTransform, actualTransform);
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String reconstructed = BurrowsWheelerTransform.inverseTransform(actualTransform.transformed, actualTransform.originalIndex);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testTransformNull() {
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assertEquals(new BurrowsWheelerTransform.BWTResult("", -1), BurrowsWheelerTransform.transform(null));
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}
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@Test
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public void testInverseTransformNullString() {
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// bwtString == null
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assertEquals("", BurrowsWheelerTransform.inverseTransform(null, 1));
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// bwtString.isEmpty()
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assertEquals("", BurrowsWheelerTransform.inverseTransform("", 0));
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}
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@Test
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public void testInverseTransformIndexOutOfBounds() {
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String bwt = "annb$aa";
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int n = bwt.length(); // n = 7
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// originalIndex >= n
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assertThrows(IllegalArgumentException.class, () -> BurrowsWheelerTransform.inverseTransform(bwt, n));
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assertThrows(IllegalArgumentException.class, () -> BurrowsWheelerTransform.inverseTransform(bwt, 8));
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// originalIndex < 0
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assertThrows(IllegalArgumentException.class, () -> BurrowsWheelerTransform.inverseTransform(bwt, -2));
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}
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@Test
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public void testBWTResultHelpers() {
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BurrowsWheelerTransform.BWTResult res1 = new BurrowsWheelerTransform.BWTResult("annb$aa", 4);
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BurrowsWheelerTransform.BWTResult res2 = new BurrowsWheelerTransform.BWTResult("annb$aa", 4);
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BurrowsWheelerTransform.BWTResult res3 = new BurrowsWheelerTransform.BWTResult("other", 4);
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BurrowsWheelerTransform.BWTResult res4 = new BurrowsWheelerTransform.BWTResult("annb$aa", 1);
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assertEquals(res1, res1);
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assertEquals(res1, res2);
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assertNotEquals(res1, null); // obj == null
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assertNotEquals(res1, new Object()); // different class
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assertNotEquals(res1, res3); // different transformed
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assertNotEquals(res1, res4); // different originalIndex
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assertEquals(res1.hashCode(), res2.hashCode());
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assertNotEquals(res1.hashCode(), res3.hashCode());
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assertTrue(res1.toString().contains("annb$aa"));
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assertTrue(res1.toString().contains("originalIndex=4"));
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}
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}
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@@ -0,0 +1,92 @@
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package com.thealgorithms.compression;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import java.util.List;
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import org.junit.jupiter.api.Test;
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public class MoveToFrontTest {
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@Test
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public void testTransformAndInverseBananaExample() {
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String original = "annb$aa";
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String alphabet = "$abn";
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List<Integer> expectedTransform = List.of(1, 3, 0, 3, 3, 3, 0);
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// Test forward transform
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List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
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assertEquals(expectedTransform, actualTransform);
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// Test inverse transform
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String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testTransformAndInverseCabaaExample() {
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String original = "cabaa";
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String alphabet = "abcdef";
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List<Integer> expectedTransform = List.of(2, 1, 2, 1, 0);
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// Test forward transform
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List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
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assertEquals(expectedTransform, actualTransform);
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// Test inverse transform
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String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testEmptyInput() {
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String original = "";
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String alphabet = "abc";
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List<Integer> expectedTransform = List.of();
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List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
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assertEquals(expectedTransform, actualTransform);
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String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
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assertEquals(original, reconstructed);
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}
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@Test
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public void testEmptyAlphabet() {
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assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abc", ""));
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assertEquals("", MoveToFront.inverseTransform(List.of(1, 2), ""));
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}
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@Test
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public void testSymbolNotInAlphabet() {
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// 'd' is not in "abc"
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assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abd", "abc"));
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}
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@Test
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public void testIndexOutOfBounds() {
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// Index 5 is out of bounds for alphabet "abc"
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// 1. test index >= alphabet.size()
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assertThrows(IllegalArgumentException.class, () -> MoveToFront.inverseTransform(List.of(1, 2, 5), "abc"));
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// 2. test index < 0
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assertThrows(IllegalArgumentException.class, () -> MoveToFront.inverseTransform(List.of(1, -1, 2), "abc"));
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}
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@Test
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public void testTransformNull() {
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List<Integer> expected = List.of();
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assertEquals(expected, MoveToFront.transform(null, "abc"));
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assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abc", null));
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}
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@Test
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public void testInverseTransformNulls() {
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// 1. test indices == null
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assertEquals("", MoveToFront.inverseTransform(null, "abc"));
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// 2. test initialAlphabet == null
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assertEquals("", MoveToFront.inverseTransform(List.of(1, 2), null));
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}
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}
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