diff --git a/DIRECTORY.md b/DIRECTORY.md
index 09407e342180..06307d4aca78 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -26,9 +26,11 @@
* [BcdConversion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BcdConversion.java)
* [BinaryPalindromeCheck](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BinaryPalindromeCheck.java)
* [BitSwap](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BitSwap.java)
+ * [BooleanAlgebraGates](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/BooleanAlgebraGates.java)
* [ClearLeftmostSetBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/ClearLeftmostSetBit.java)
* [CountLeadingZeros](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/CountLeadingZeros.java)
* [CountSetBits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/CountSetBits.java)
+ * [FindNthBit](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/FindNthBit.java)
* [GrayCodeConversion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/GrayCodeConversion.java)
* [HammingDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/HammingDistance.java)
* [HigherLowerPowerOfTwo](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwo.java)
@@ -56,6 +58,7 @@
* [CompositeLFSR](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/a5/CompositeLFSR.java)
* [LFSR](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/a5/LFSR.java)
* [Utils](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/a5/Utils.java)
+ * [ADFGVXCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/ADFGVXCipher.java)
* [AES](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AES.java)
* [AESEncryption](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AESEncryption.java)
* [AffineCipher](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/ciphers/AffineCipher.java)
@@ -135,6 +138,7 @@
* [FordFulkerson](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/FordFulkerson.java)
* [Graphs](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/Graphs.java)
* [HamiltonianCycle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/HamiltonianCycle.java)
+ * [JohnsonsAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/JohnsonsAlgorithm.java)
* [KahnsAlgorithm](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/KahnsAlgorithm.java)
* [Kosaraju](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/Kosaraju.java)
* [Kruskal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/datastructures/graphs/Kruskal.java)
@@ -342,6 +346,7 @@
* [EulersFunction](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/EulersFunction.java)
* [Factorial](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/Factorial.java)
* [FactorialRecursion](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FactorialRecursion.java)
+ * [FastExponentiation](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FastExponentiation.java)
* [FastInverseSqrt](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FastInverseSqrt.java)
* [FFT](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FFT.java)
* [FFTBluestein](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/FFTBluestein.java)
@@ -659,9 +664,11 @@
* [BcdConversionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BcdConversionTest.java)
* [BinaryPalindromeCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BinaryPalindromeCheckTest.java)
* [BitSwapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BitSwapTest.java)
+ * [BooleanAlgebraGatesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/BooleanAlgebraGatesTest.java)
* [ClearLeftmostSetBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/ClearLeftmostSetBitTest.java)
* [CountLeadingZerosTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/CountLeadingZerosTest.java)
* [CountSetBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/CountSetBitsTest.java)
+ * [FindNthBitTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/FindNthBitTest.java)
* [GrayCodeConversionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/GrayCodeConversionTest.java)
* [HammingDistanceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/HammingDistanceTest.java)
* [HigherLowerPowerOfTwoTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/HigherLowerPowerOfTwoTest.java)
@@ -680,12 +687,13 @@
* [SingleElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/SingleElementTest.java)
* [SwapAdjacentBitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/SwapAdjacentBitsTest.java)
* [TwosComplementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/TwosComplementTest.java)
- * [Xs3ConversionTest](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/bitmanipulation/Xs3ConversionTest.java)
+ * [Xs3ConversionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/bitmanipulation/Xs3ConversionTest.java)
* ciphers
* a5
* [A5CipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/a5/A5CipherTest.java)
* [A5KeyStreamGeneratorTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/a5/A5KeyStreamGeneratorTest.java)
* [LFSRTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/a5/LFSRTest.java)
+ * [ADFGVXCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/ADFGVXCipherTest.java)
* [AESEncryptionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AESEncryptionTest.java)
* [AffineCipherTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AffineCipherTest.java)
* [AtbashTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/ciphers/AtbashTest.java)
@@ -754,6 +762,7 @@
* [FloydWarshallTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java)
* [FordFulkersonTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FordFulkersonTest.java)
* [HamiltonianCycleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/HamiltonianCycleTest.java)
+ * [JohnsonsAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/JohnsonsAlgorithmTest.java)
* [KosarajuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/KosarajuTest.java)
* [TarjansAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/TarjansAlgorithmTest.java)
* [WelshPowellTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/WelshPowellTest.java)
@@ -906,6 +915,7 @@
* [EulersFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/EulersFunctionTest.java)
* [FactorialRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FactorialRecursionTest.java)
* [FactorialTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FactorialTest.java)
+ * [FastExponentiationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FastExponentiationTest.java)
* [FastInverseSqrtTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FastInverseSqrtTests.java)
* [FFTTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FFTTest.java)
* [FibonacciJavaStreamsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/FibonacciJavaStreamsTest.java)
@@ -1014,6 +1024,7 @@
* [SkylineProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/SkylineProblemTest.java)
* [SudokuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/SudokuTest.java)
* [TestPrintMatrixInSpiralOrder](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/TestPrintMatrixInSpiralOrder.java)
+ * [TowerOfHanoiTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java)
* [TwoPointersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/TwoPointersTest.java)
* [WorstFitCPUTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/others/WorstFitCPUTest.java)
* Recursion
diff --git a/src/main/java/com/thealgorithms/others/TowerOfHanoi.java b/src/main/java/com/thealgorithms/others/TowerOfHanoi.java
index 2216799b987a..7017ed03f843 100644
--- a/src/main/java/com/thealgorithms/others/TowerOfHanoi.java
+++ b/src/main/java/com/thealgorithms/others/TowerOfHanoi.java
@@ -1,29 +1,65 @@
package com.thealgorithms.others;
-import java.util.Scanner;
+import java.util.List;
+/**
+ * The {@code TowerOfHanoi} class provides a recursive solution to the Tower of Hanoi puzzle.
+ * This puzzle involves moving a set of discs from one pole to another, following specific rules:
+ * 1. Only one disc can be moved at a time.
+ * 2. A disc can only be placed on top of a larger disc.
+ * 3. All discs must start on one pole and end on another.
+ *
+ * This implementation recursively calculates the steps required to solve the puzzle and stores them
+ * in a provided list.
+ *
+ *
+ * For more information about the Tower of Hanoi, see
+ * Tower of Hanoi on Wikipedia.
+ *
+ *
+ * The {@code shift} method takes the number of discs and the names of the poles,
+ * and appends the steps required to solve the puzzle to the provided list.
+ * Time Complexity: O(2^n) - Exponential time complexity due to the recursive nature of the problem.
+ * Space Complexity: O(n) - Linear space complexity due to the recursion stack.
+ * Wikipedia: https://en.wikipedia.org/wiki/Tower_of_Hanoi
+ */
final class TowerOfHanoi {
+
private TowerOfHanoi() {
}
- public static void shift(int n, String startPole, String intermediatePole, String endPole) {
- // if n becomes zero the program returns thus ending the loop.
+ /**
+ * Recursively solve the Tower of Hanoi puzzle by moving discs between poles.
+ *
+ * @param n The number of discs to move.
+ * @param startPole The name of the start pole from which discs are moved.
+ * @param intermediatePole The name of the intermediate pole used as a temporary holding area.
+ * @param endPole The name of the end pole to which discs are moved.
+ * @param result A list to store the steps required to solve the puzzle.
+ *
+ *
+ * This method is called recursively to move n-1 discs
+ * to the intermediate pole,
+ * then moves the nth disc to the end pole, and finally
+ * moves the n-1 discs from the
+ * intermediate pole to the end pole.
+ *
+ *
+ *
+ * Time Complexity: O(2^n) - Exponential time complexity due to the recursive nature of the problem.
+ * Space Complexity: O(n) - Linear space complexity due to the recursion stack.
+ *
+ */
+ public static void shift(int n, String startPole, String intermediatePole, String endPole, List result) {
if (n != 0) {
- // Shift function is called in recursion for swapping the n-1 disc from the startPole to
- // the intermediatePole
- shift(n - 1, startPole, endPole, intermediatePole);
- System.out.format("Move %d from %s to %s%n", n, startPole, endPole); // Result Printing
- // Shift function is called in recursion for swapping the n-1 disc from the
- // intermediatePole to the endPole
- shift(n - 1, intermediatePole, startPole, endPole);
- }
- }
+ // Move n-1 discs from startPole to intermediatePole
+ shift(n - 1, startPole, endPole, intermediatePole, result);
- public static void main(String[] args) {
- System.out.print("Enter number of discs on Pole 1: ");
- Scanner scanner = new Scanner(System.in);
- int numberOfDiscs = scanner.nextInt(); // input of number of discs on pole 1
- shift(numberOfDiscs, "Pole1", "Pole2", "Pole3"); // Shift function called
- scanner.close();
+ // Add the move of the nth disc from startPole to endPole
+ result.add(String.format("Move %d from %s to %s", n, startPole, endPole));
+
+ // Move the n-1 discs from intermediatePole to endPole
+ shift(n - 1, intermediatePole, startPole, endPole, result);
+ }
}
}
diff --git a/src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java b/src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java
new file mode 100644
index 000000000000..ca9376dd48eb
--- /dev/null
+++ b/src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java
@@ -0,0 +1,50 @@
+package com.thealgorithms.others;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class TowerOfHanoiTest {
+
+ @Test
+ public void testHanoiWithOneDisc() {
+ List result = new ArrayList<>();
+ TowerOfHanoi.shift(1, "Pole1", "Pole2", "Pole3", result);
+
+ // Expected output for 1 disc
+ List expected = List.of("Move 1 from Pole1 to Pole3");
+ assertEquals(expected, result);
+ }
+
+ @Test
+ public void testHanoiWithTwoDiscs() {
+ List result = new ArrayList<>();
+ TowerOfHanoi.shift(2, "Pole1", "Pole2", "Pole3", result);
+
+ // Expected output for 2 discs
+ List expected = List.of("Move 1 from Pole1 to Pole2", "Move 2 from Pole1 to Pole3", "Move 1 from Pole2 to Pole3");
+ assertEquals(expected, result);
+ }
+
+ @Test
+ public void testHanoiWithThreeDiscs() {
+ List result = new ArrayList<>();
+ TowerOfHanoi.shift(3, "Pole1", "Pole2", "Pole3", result);
+
+ // Expected output for 3 discs
+ List expected = List.of("Move 1 from Pole1 to Pole3", "Move 2 from Pole1 to Pole2", "Move 1 from Pole3 to Pole2", "Move 3 from Pole1 to Pole3", "Move 1 from Pole2 to Pole1", "Move 2 from Pole2 to Pole3", "Move 1 from Pole1 to Pole3");
+ assertEquals(expected, result);
+ }
+
+ @Test
+ public void testHanoiWithZeroDiscs() {
+ List result = new ArrayList<>();
+ TowerOfHanoi.shift(0, "Pole1", "Pole2", "Pole3", result);
+
+ // There should be no moves if there are 0 discs
+ assertTrue(result.isEmpty());
+ }
+}