refactor: QueueUsingTwoStacks (#5427)
refactor: QueueUsingTwoStacks Co-authored-by: alxkm <alx@alx.com>
This commit is contained in:
Alex Klymenko
GitHub
parent
203d544668
commit
6b7a1fdbe8
@ -15,17 +15,14 @@ import java.util.Stack;
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*
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* @author sahilb2 (https://www.github.com/sahilb2)
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*/
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class QueueWithStack {
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// Stack to keep track of elements inserted into the queue
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private Stack<Object> inStack;
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// Stack to keep track of elements to be removed next in queue
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private Stack<Object> outStack;
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public class QueueUsingTwoStacks {
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private final Stack<Object> inStack;
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private final Stack<Object> outStack;
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/**
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* Constructor
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*/
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QueueWithStack() {
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public QueueUsingTwoStacks() {
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this.inStack = new Stack<>();
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this.outStack = new Stack<>();
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}
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@ -94,7 +91,7 @@ class QueueWithStack {
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* @return true if the inStack is empty.
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*/
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public boolean isInStackEmpty() {
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return (inStack.size() == 0);
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return (inStack.isEmpty());
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}
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/**
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@ -103,73 +100,6 @@ class QueueWithStack {
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* @return true if the outStack is empty.
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*/
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public boolean isOutStackEmpty() {
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return (outStack.size() == 0);
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}
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}
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/**
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* This class is the example for the Queue class
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*
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* @author sahilb2 (https://www.github.com/sahilb2)
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*/
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public final class QueueUsingTwoStacks {
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private QueueUsingTwoStacks() {
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}
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/**
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* Main method
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*
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* @param args Command line arguments
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*/
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public static void main(String[] args) {
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QueueWithStack myQueue = new QueueWithStack();
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myQueue.insert(1);
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System.out.println(myQueue.peekBack()); // Will print 1
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// instack: [(top) 1]
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// outStack: []
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myQueue.insert(2);
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System.out.println(myQueue.peekBack()); // Will print 2
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// instack: [(top) 2, 1]
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// outStack: []
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myQueue.insert(3);
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System.out.println(myQueue.peekBack()); // Will print 3
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// instack: [(top) 3, 2, 1]
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// outStack: []
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myQueue.insert(4);
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System.out.println(myQueue.peekBack()); // Will print 4
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// instack: [(top) 4, 3, 2, 1]
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// outStack: []
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System.out.println(myQueue.isEmpty()); // Will print false
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System.out.println(myQueue.remove()); // Will print 1
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System.out.println((myQueue.isInStackEmpty()) ? "null" : myQueue.peekBack()); // Will print NULL
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// instack: []
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// outStack: [(top) 2, 3, 4]
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myQueue.insert(5);
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System.out.println(myQueue.peekFront()); // Will print 2
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// instack: [(top) 5]
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// outStack: [(top) 2, 3, 4]
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myQueue.remove();
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System.out.println(myQueue.peekFront()); // Will print 3
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// instack: [(top) 5]
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// outStack: [(top) 3, 4]
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myQueue.remove();
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System.out.println(myQueue.peekFront()); // Will print 4
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// instack: [(top) 5]
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// outStack: [(top) 4]
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myQueue.remove();
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// instack: [(top) 5]
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// outStack: []
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System.out.println(myQueue.peekFront()); // Will print 5
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// instack: []
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// outStack: [(top) 5]
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myQueue.remove();
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// instack: []
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// outStack: []
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System.out.println(myQueue.isEmpty()); // Will print true
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return (outStack.isEmpty());
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}
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}
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@ -0,0 +1,145 @@
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package com.thealgorithms.others;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.util.EmptyStackException;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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class QueueUsingTwoStacksTest {
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private QueueUsingTwoStacks queue;
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@BeforeEach
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void setUp() {
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queue = new QueueUsingTwoStacks();
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}
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@Test
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void testIsEmptyInitially() {
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assertTrue(queue.isEmpty(), "Queue should be empty initially");
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}
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@Test
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void testInsertSingleElement() {
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queue.insert(1);
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assertFalse(queue.isEmpty(), "Queue should not be empty after inserting an element");
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assertEquals(1, queue.peekFront(), "The front element should be the inserted element");
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}
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@Test
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void testRemoveSingleElement() {
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queue.insert(1);
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assertEquals(1, queue.remove(), "Removing should return the first inserted element");
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assertTrue(queue.isEmpty(), "Queue should be empty after removing the only element");
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}
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@Test
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void testRemoveMultipleElements() {
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queue.insert(1);
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queue.insert(2);
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queue.insert(3);
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assertEquals(1, queue.remove(), "First removed element should be the first inserted element");
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assertEquals(2, queue.remove(), "Second removed element should be the second inserted element");
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assertEquals(3, queue.remove(), "Third removed element should be the third inserted element");
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assertTrue(queue.isEmpty(), "Queue should be empty after removing all elements");
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}
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@Test
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void testPeekFrontWithMultipleElements() {
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queue.insert(1);
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queue.insert(2);
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queue.insert(3);
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assertEquals(1, queue.peekFront(), "The front element should be the first inserted element");
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}
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@Test
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void testPeekBackWithMultipleElements() {
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queue.insert(1);
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queue.insert(2);
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queue.insert(3);
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assertEquals(3, queue.peekBack(), "The back element should be the last inserted element");
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}
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@Test
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void testPeekFrontAfterRemovals() {
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queue.insert(1);
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queue.insert(2);
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queue.insert(3);
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queue.remove();
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assertEquals(2, queue.peekFront(), "After removing one element, the front should be the second element");
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}
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@Test
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void testIsEmptyAfterRemovals() {
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queue.insert(1);
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queue.insert(2);
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queue.remove();
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queue.remove();
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assertTrue(queue.isEmpty(), "Queue should be empty after removing all elements");
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}
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@Test
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void testRemoveFromEmptyQueue() {
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org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::remove, "Removing from an empty queue should throw an exception");
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}
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@Test
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void testPeekFrontFromEmptyQueue() {
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org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::peekFront, "Peeking front from an empty queue should throw an exception");
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}
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@Test
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void testPeekBackFromEmptyQueue() {
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org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::peekBack, "Peeking back from an empty queue should throw an exception");
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}
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@Test
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void testIsInStackEmptyInitially() {
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assertTrue(queue.isInStackEmpty(), "inStack should be empty initially");
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}
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@Test
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void testIsOutStackEmptyInitially() {
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assertTrue(queue.isOutStackEmpty(), "outStack should be empty initially");
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}
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@Test
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void testIsInStackEmptyAfterInsertion() {
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queue.insert(1);
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assertFalse(queue.isInStackEmpty(), "inStack should not be empty after an insertion");
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}
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@Test
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void testIsOutStackEmptyAfterInsertion() {
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queue.insert(1);
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assertTrue(queue.isOutStackEmpty(), "outStack should still be empty after an insertion");
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}
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@Test
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void testIsOutStackEmptyAfterRemoval() {
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queue.insert(1);
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queue.remove();
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assertTrue(queue.isOutStackEmpty(), "outStack should be empty after removing the only element");
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}
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@Test
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void testIsInStackEmptyAfterMultipleRemovals() {
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queue.insert(1);
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queue.insert(2);
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queue.remove();
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queue.remove();
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assertTrue(queue.isInStackEmpty(), "inStack should be empty after removing all elements");
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}
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@Test
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void testIsOutStackEmptyAfterMultipleRemovals() {
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queue.insert(1);
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queue.insert(2);
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queue.remove();
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queue.remove();
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assertTrue(queue.isOutStackEmpty(), "outStack should be empty after removing all elements");
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}
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}
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