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Add function documentation, enhance comments in TowerOfHanoi.java #5533
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Add function documentation, enhance comments in TowerOfHanoi.java
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Add unit tests for ToH
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,29 +1,65 @@ | ||
| package com.thealgorithms.others; | ||
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| import java.util.Scanner; | ||
| import java.util.List; | ||
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| /** | ||
| * 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. | ||
| * | ||
| * <p> | ||
| * For more information about the Tower of Hanoi, see | ||
| * <a href="https://en.wikipedia.org/wiki/Tower_of_Hanoi">Tower of Hanoi on Uncyclopedia</a>. | ||
| * </p> | ||
| * | ||
| * 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. | ||
| * Uncyclopedia: https://en.wikipedia.org/wiki/Tower_of_Hanoi | ||
| */ | ||
| final class TowerOfHanoi { | ||
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| private TowerOfHanoi() { | ||
| } | ||
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| 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. | ||
| * | ||
| * <p> | ||
| * 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. | ||
| * </p> | ||
| * | ||
| * <p> | ||
| * 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. | ||
| * </p> | ||
| */ | ||
| public static void shift(int n, String startPole, String intermediatePole, String endPole, List<String> result) { | ||
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|
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| 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); | ||
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| 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)); | ||
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| // Move the n-1 discs from intermediatePole to endPole | ||
| shift(n - 1, intermediatePole, startPole, endPole, result); | ||
| } | ||
| } | ||
| } | ||
50 changes: 50 additions & 0 deletions
50
src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| package com.thealgorithms.others; | ||
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| import static org.junit.jupiter.api.Assertions.assertEquals; | ||
| import static org.junit.jupiter.api.Assertions.assertTrue; | ||
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| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import org.junit.jupiter.api.Test; | ||
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| public class TowerOfHanoiTest { | ||
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| @Test | ||
| public void testHanoiWithOneDisc() { | ||
| List<String> result = new ArrayList<>(); | ||
| TowerOfHanoi.shift(1, "Pole1", "Pole2", "Pole3", result); | ||
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| // Expected output for 1 disc | ||
| List<String> expected = List.of("Move 1 from Pole1 to Pole3"); | ||
| assertEquals(expected, result); | ||
| } | ||
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| @Test | ||
| public void testHanoiWithTwoDiscs() { | ||
| List<String> result = new ArrayList<>(); | ||
| TowerOfHanoi.shift(2, "Pole1", "Pole2", "Pole3", result); | ||
|
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| // Expected output for 2 discs | ||
| List<String> expected = List.of("Move 1 from Pole1 to Pole2", "Move 2 from Pole1 to Pole3", "Move 1 from Pole2 to Pole3"); | ||
| assertEquals(expected, result); | ||
| } | ||
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| @Test | ||
| public void testHanoiWithThreeDiscs() { | ||
| List<String> result = new ArrayList<>(); | ||
| TowerOfHanoi.shift(3, "Pole1", "Pole2", "Pole3", result); | ||
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| // Expected output for 3 discs | ||
| List<String> 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); | ||
| } | ||
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| @Test | ||
| public void testHanoiWithZeroDiscs() { | ||
| List<String> result = new ArrayList<>(); | ||
| TowerOfHanoi.shift(0, "Pole1", "Pole2", "Pole3", result); | ||
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| // There should be no moves if there are 0 discs | ||
| assertTrue(result.isEmpty()); | ||
| } | ||
| } |
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