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Enhance docs, add tests in StackOfLinkedList (#6021)

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This commit is contained in:
Hardik Pawar
2024-10-26 11:28:11 +05:30
committed by GitHub
parent 0f1dcbe479
commit 6684a6993e
4 changed files with 167 additions and 123 deletions
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4
DIRECTORY.md
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@ -571,6 +571,7 @@
* [UnionFind](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/UnionFind.java)
* [UpperBound](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/searches/UpperBound.java)
* slidingwindow
* [LongestSubstringWithoutRepeatingCharacters](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/slidingwindow/LongestSubstringWithoutRepeatingCharacters.java)
* [MaxSumKSizeSubarray](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/slidingwindow/MaxSumKSizeSubarray.java)
* sorts
* [AdaptiveMergeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/AdaptiveMergeSort.java)
@ -855,9 +856,9 @@
* [QueueByTwoStacksTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/QueueByTwoStacksTest.java)
* [QueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/queues/QueueTest.java)
* stacks
* [LinkedListStackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/LinkedListStackTest.java)
* [StackArrayListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackArrayListTest.java)
* [StackArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackArrayTest.java)
* [StackOfLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackOfLinkedListTest.java)
* trees
* [BinaryTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java)
* [BoundaryTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BoundaryTraversalTest.java)
@ -1163,6 +1164,7 @@
* [UnionFindTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/UnionFindTest.java)
* [UpperBoundTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/UpperBoundTest.java)
* slidingwindow
* [LongestSubstringWithoutRepeatingCharactersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/slidingwindow/LongestSubstringWithoutRepeatingCharactersTest.java)
* [MaxSumKSizeSubarrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/slidingwindow/MaxSumKSizeSubarrayTest.java)
* sorts
* [AdaptiveMergeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/AdaptiveMergeSortTest.java)

94
src/main/java/com/thealgorithms/datastructures/stacks/StackOfLinkedList.java
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@ -3,35 +3,20 @@ package com.thealgorithms.datastructures.stacks;
import java.util.NoSuchElementException;
/**
* @author Varun Upadhyay (https://github.com/varunu28)
* A stack implementation using a singly linked list.
*
* <p>This class provides methods to push, pop, and peek elements in a Last-In-First-Out (LIFO) manner.
* It keeps track of the number of elements in the stack and allows checking if the stack is empty.
*
* <p>This implementation does not allow null elements to be pushed onto the stack.
*/
// An implementation of a Stack using a Linked List
final class StackOfLinkedList {
private StackOfLinkedList() {
}
public static void main(String[] args) {
LinkedListStack stack = new LinkedListStack();
stack.push(1);
stack.push(2);
stack.push(3);
stack.push(4);
stack.push(5);
System.out.println(stack);
System.out.println("Size of stack currently is: " + stack.getSize());
assert stack.pop() == 5;
assert stack.pop() == 4;
System.out.println("Top element of stack currently is: " + stack.peek());
}
}
// A node class
// A node class for the linked list
class Node {
public int data;
public Node next;
@ -42,25 +27,24 @@ class Node {
}
/**
* A class which implements a stack using a linked list
* A class that implements a stack using a linked list.
*
* <p>
* Contains all the stack methods : push, pop, printStack, isEmpty
* <p>This stack supports basic operations:
* <ul>
* <li>push: Adds an element to the top of the stack</li>
* <li>pop: Removes and returns the top element of the stack</li>
* <li>peek: Returns the top element without removing it</li>
* <li>isEmpty: Checks if the stack is empty</li>
* <li>getSize: Returns the current size of the stack</li>
* </ul>
*/
class LinkedListStack {
/**
* Top of stack
*/
Node head;
private Node head; // Top of the stack
private int size; // Number of elements in the stack
/**
* Size of stack
*/
private int size;
/**
* Init properties
* Initializes an empty stack.
*/
LinkedListStack() {
head = null;
@ -68,10 +52,10 @@ class LinkedListStack {
}
/**
* Add element at top
* Adds an element to the top of the stack.
*
* @param x to be added
* @return <tt>true</tt> if add successfully
* @param x the element to be added
* @return <tt>true</tt> if the element is added successfully
*/
public boolean push(int x) {
Node newNode = new Node(x);
@ -82,10 +66,10 @@ class LinkedListStack {
}
/**
* Pop element at top of stack
* Removes and returns the top element of the stack.
*
* @return element at top of stack
* @throws NoSuchElementException if stack is empty
* @return the element at the top of the stack
* @throws NoSuchElementException if the stack is empty
*/
public int pop() {
if (size == 0) {
@ -94,20 +78,20 @@ class LinkedListStack {
Node destroy = head;
head = head.next;
int retValue = destroy.data;
destroy = null; // clear to let GC do it's work
destroy = null; // Help garbage collection
size--;
return retValue;
}
/**
* Peek element at top of stack
* Returns the top element of the stack without removing it.
*
* @return element at top of stack
* @throws NoSuchElementException if stack is empty
* @return the element at the top of the stack
* @throws NoSuchElementException if the stack is empty
*/
public int peek() {
if (size == 0) {
throw new NoSuchElementException("Empty stack. Nothing to pop");
throw new NoSuchElementException("Empty stack. Nothing to peek");
}
return head.data;
}
@ -120,24 +104,32 @@ class LinkedListStack {
builder.append(cur.data).append("->");
cur = cur.next;
}
return builder.replace(builder.length() - 2, builder.length(), "").toString();
return builder.replace(builder.length() - 2, builder.length(), "").toString(); // Remove the last "->"
}
/**
* Check if stack is empty
* Checks if the stack is empty.
*
* @return <tt>true</tt> if stack is empty, otherwise <tt>false</tt>
* @return <tt>true</tt> if the stack is empty, <tt>false</tt> otherwise
*/
public boolean isEmpty() {
return size == 0;
}
/**
* Return size of stack
* Returns the current size of the stack.
*
* @return size of stack
* @return the number of elements in the stack
*/
public int getSize() {
return size;
}
/**
* Removes all elements from the stack.
*/
public void makeEmpty() {
head = null;
size = 0;
}
}

71
src/test/java/com/thealgorithms/datastructures/stacks/LinkedListStackTest.java
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@ -1,71 +0,0 @@
package com.thealgorithms.datastructures.stacks;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.NoSuchElementException;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
public class LinkedListStackTest {
private LinkedListStack stack;
@BeforeEach
public void setUp() {
stack = new LinkedListStack();
}
@Test
public void testPushAndPeek() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals(3, stack.peek());
assertEquals(3, stack.getSize());
}
@Test
public void testPop() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals(3, stack.pop());
assertEquals(2, stack.pop());
assertEquals(1, stack.pop());
assertTrue(stack.isEmpty());
}
@Test
public void testPopEmptyStack() {
org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, () -> stack.pop());
}
@Test
public void testPeekEmptyStack() {
org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, () -> stack.peek());
}
@Test
public void testIsEmpty() {
assertTrue(stack.isEmpty());
stack.push(1);
assertFalse(stack.isEmpty());
stack.pop();
assertTrue(stack.isEmpty());
}
@Test
public void testToString() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals("3->2->1", stack.toString());
}
}

121
src/test/java/com/thealgorithms/datastructures/stacks/StackOfLinkedListTest.java Normal file
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@ -0,0 +1,121 @@
package com.thealgorithms.datastructures.stacks;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.NoSuchElementException;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
public class StackOfLinkedListTest {
private LinkedListStack stack;
@BeforeEach
public void setUp() {
stack = new LinkedListStack();
}
@Test
public void testPushAndPeek() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals(3, stack.peek(), "Peek should return the last pushed value");
assertEquals(3, stack.getSize(), "Size should reflect the number of elements");
}
@Test
public void testPop() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals(3, stack.pop(), "Pop should return the last pushed value");
assertEquals(2, stack.pop(), "Pop should return the next last pushed value");
assertEquals(1, stack.pop(), "Pop should return the first pushed value");
assertTrue(stack.isEmpty(), "Stack should be empty after popping all elements");
}
@Test
public void testPopEmptyStack() {
org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, () -> stack.pop(), "Popping from an empty stack should throw NoSuchElementException");
}
@Test
public void testPeekEmptyStack() {
org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, () -> stack.peek(), "Peeking into an empty stack should throw NoSuchElementException");
}
@Test
public void testIsEmpty() {
assertTrue(stack.isEmpty(), "Newly created stack should be empty");
stack.push(1);
assertFalse(stack.isEmpty(), "Stack should not be empty after pushing an element");
stack.pop();
assertTrue(stack.isEmpty(), "Stack should be empty after popping the only element");
}
@Test
public void testToString() {
stack.push(1);
stack.push(2);
stack.push(3);
assertEquals("3->2->1", stack.toString(), "String representation of stack should match the expected format");
}
@Test
public void testMultiplePushesAndPops() {
stack.push(5);
stack.push(10);
stack.push(15);
assertEquals(15, stack.pop(), "Pop should return the last pushed value");
assertEquals(10, stack.peek(), "Peek should return the new top value after popping");
assertEquals(10, stack.pop(), "Pop should return the next last pushed value");
assertEquals(5, stack.pop(), "Pop should return the first pushed value");
assertTrue(stack.isEmpty(), "Stack should be empty after popping all elements");
}
@Test
public void testGetSize() {
assertEquals(0, stack.getSize(), "Size of an empty stack should be zero");
stack.push(1);
stack.push(2);
assertEquals(2, stack.getSize(), "Size should reflect the number of elements");
stack.pop();
assertEquals(1, stack.getSize(), "Size should decrease with each pop");
}
@Test
public void testSizeAfterClearingStack() {
stack.push(1);
stack.push(2);
stack.push(3);
// Manually clear the stack
while (!stack.isEmpty()) {
stack.pop();
}
assertTrue(stack.isEmpty(), "Stack should be empty after clearing");
assertEquals(0, stack.getSize(), "Size should be zero after clearing the stack");
}
@Test
public void testSequentialPushAndPop() {
for (int i = 1; i <= 100; i++) {
stack.push(i);
}
assertEquals(100, stack.getSize(), "Size should be 100 after pushing 100 elements");
for (int i = 100; i >= 1; i--) {
assertEquals(i, stack.pop(), "Popping should return values in LIFO order");
}
assertTrue(stack.isEmpty(), "Stack should be empty after popping all elements");
}
}