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feat(compression): Add Burrows-Wheeler Transform (BWT) and Move-to-Front (MTF) (#6926)

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* feat(compression): Add Burrows-Wheeler Transform (BWT) and Move-to-Front (MTF)

* Resolve SpotBugs

* fix code style
This commit is contained in:
Indolyn Yi
2025-10-25 17:29:45 +08:00
committed by GitHub
parent 48ba1ae466
commit ab65ac6485
4 changed files with 600 additions and 0 deletions
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src/test/java/com/thealgorithms/compression/MoveToFrontTest.java Normal file
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package com.thealgorithms.compression;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import java.util.List;
import org.junit.jupiter.api.Test;
public class MoveToFrontTest {
@Test
public void testTransformAndInverseBananaExample() {
String original = "annb$aa";
String alphabet = "$abn";
List<Integer> expectedTransform = List.of(1, 3, 0, 3, 3, 3, 0);
// Test forward transform
List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
assertEquals(expectedTransform, actualTransform);
// Test inverse transform
String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
assertEquals(original, reconstructed);
}
@Test
public void testTransformAndInverseCabaaExample() {
String original = "cabaa";
String alphabet = "abcdef";
List<Integer> expectedTransform = List.of(2, 1, 2, 1, 0);
// Test forward transform
List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
assertEquals(expectedTransform, actualTransform);
// Test inverse transform
String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
assertEquals(original, reconstructed);
}
@Test
public void testEmptyInput() {
String original = "";
String alphabet = "abc";
List<Integer> expectedTransform = List.of();
List<Integer> actualTransform = MoveToFront.transform(original, alphabet);
assertEquals(expectedTransform, actualTransform);
String reconstructed = MoveToFront.inverseTransform(actualTransform, alphabet);
assertEquals(original, reconstructed);
}
@Test
public void testEmptyAlphabet() {
assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abc", ""));
assertEquals("", MoveToFront.inverseTransform(List.of(1, 2), ""));
}
@Test
public void testSymbolNotInAlphabet() {
// 'd' is not in "abc"
assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abd", "abc"));
}
@Test
public void testIndexOutOfBounds() {
// Index 5 is out of bounds for alphabet "abc"
// 1. test index >= alphabet.size()
assertThrows(IllegalArgumentException.class, () -> MoveToFront.inverseTransform(List.of(1, 2, 5), "abc"));
// 2. test index < 0
assertThrows(IllegalArgumentException.class, () -> MoveToFront.inverseTransform(List.of(1, -1, 2), "abc"));
}
@Test
public void testTransformNull() {
List<Integer> expected = List.of();
assertEquals(expected, MoveToFront.transform(null, "abc"));
assertThrows(IllegalArgumentException.class, () -> MoveToFront.transform("abc", null));
}
@Test
public void testInverseTransformNulls() {
// 1. test indices == null
assertEquals("", MoveToFront.inverseTransform(null, "abc"));
// 2. test initialAlphabet == null
assertEquals("", MoveToFront.inverseTransform(List.of(1, 2), null));
}
}