Add Tower of Hanoi recursive algorithm (#7235)

* Add Tower of Hanoi recursive algorithm with tests

* Fix SpotBugs issues and format TowerOfHanoi tests

* Enhance existing TowerOfHanoi and remove duplicate recursion version

* Fix clang-format issue

---------

Co-authored-by: Deniz Altunkapan <deniz.altunkapan@outlook.com>
This commit is contained in:
Mohammed Vijahath
2026-02-11 20:30:15 +05:30
committed by GitHub
parent 8403b8feb1
commit 0c79d33eb5
2 changed files with 67 additions and 24 deletions

View File

@@ -1,14 +1,31 @@
package com.thealgorithms.puzzlesandgames;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;
public class TowerOfHanoiTest {
@ParameterizedTest
@MethodSource("diskCountAndMoveCount")
void testMoveCountMatchesFormula(int disks, int expectedMoves) {
List<String> result = new ArrayList<>();
TowerOfHanoi.shift(disks, "A", "B", "C", result);
assertEquals(expectedMoves, result.size());
}
private static Stream<Arguments> diskCountAndMoveCount() {
return Stream.of(Arguments.of(1, 1), Arguments.of(2, 3), Arguments.of(3, 7), Arguments.of(4, 15), Arguments.of(5, 31), Arguments.of(10, 1023));
}
@Test
public void testHanoiWithOneDisc() {
List<String> result = new ArrayList<>();
@@ -39,6 +56,15 @@ public class TowerOfHanoiTest {
assertEquals(expected, result);
}
@Test
public void testHanoiWithDifferentPoles() {
List<String> result = new ArrayList<>();
TowerOfHanoi.shift(2, "X", "Y", "Z", result);
List<String> expected = List.of("Move 1 from X to Y", "Move 2 from X to Z", "Move 1 from Y to Z");
assertEquals(expected, result);
}
@Test
public void testHanoiWithZeroDiscs() {
List<String> result = new ArrayList<>();
@@ -47,4 +73,10 @@ public class TowerOfHanoiTest {
// There should be no moves if there are 0 discs
assertTrue(result.isEmpty());
}
@Test
public void testHanoiWithNegativeDiscsThrows() {
List<String> result = new ArrayList<>();
assertThrows(IllegalArgumentException.class, () -> TowerOfHanoi.shift(-1, "Pole1", "Pole2", "Pole3", result));
}
}