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alxkmalxkm
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Merge branch 'master' into refactor/CountWords
2 parents 3565d51 + 6b7a1fd commit 35cb01f

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2 files changed

+151
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‎src/main/java/com/thealgorithms/others/QueueUsingTwoStacks.java

+6-76
Original file line numberDiff line numberDiff line change
@@ -15,17 +15,14 @@
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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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}
@@ -94,7 +91,7 @@ public boolean isEmpty() {
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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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/**
@@ -103,73 +100,6 @@ public boolean isInStackEmpty() {
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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
103+
return (outStack.isEmpty());
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}
175105
}

‎src/test/java/com/thealgorithms/others/QueueUsingTwoStacksTest.java

+145
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,145 @@
1+
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;
5+
import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.util.EmptyStackException;
8+
import org.junit.jupiter.api.BeforeEach;
9+
import org.junit.jupiter.api.Test;
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class QueueUsingTwoStacksTest {
12+
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private QueueUsingTwoStacks queue;
14+
15+
@BeforeEach
16+
void setUp() {
17+
queue = new QueueUsingTwoStacks();
18+
}
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20+
@Test
21+
void testIsEmptyInitially() {
22+
assertTrue(queue.isEmpty(), "Queue should be empty initially");
23+
}
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@Test
26+
void testInsertSingleElement() {
27+
queue.insert(1);
28+
assertFalse(queue.isEmpty(), "Queue should not be empty after inserting an element");
29+
assertEquals(1, queue.peekFront(), "The front element should be the inserted element");
30+
}
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32+
@Test
33+
void testRemoveSingleElement() {
34+
queue.insert(1);
35+
assertEquals(1, queue.remove(), "Removing should return the first inserted element");
36+
assertTrue(queue.isEmpty(), "Queue should be empty after removing the only element");
37+
}
38+
39+
@Test
40+
void testRemoveMultipleElements() {
41+
queue.insert(1);
42+
queue.insert(2);
43+
queue.insert(3);
44+
assertEquals(1, queue.remove(), "First removed element should be the first inserted element");
45+
assertEquals(2, queue.remove(), "Second removed element should be the second inserted element");
46+
assertEquals(3, queue.remove(), "Third removed element should be the third inserted element");
47+
assertTrue(queue.isEmpty(), "Queue should be empty after removing all elements");
48+
}
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50+
@Test
51+
void testPeekFrontWithMultipleElements() {
52+
queue.insert(1);
53+
queue.insert(2);
54+
queue.insert(3);
55+
assertEquals(1, queue.peekFront(), "The front element should be the first inserted element");
56+
}
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58+
@Test
59+
void testPeekBackWithMultipleElements() {
60+
queue.insert(1);
61+
queue.insert(2);
62+
queue.insert(3);
63+
assertEquals(3, queue.peekBack(), "The back element should be the last inserted element");
64+
}
65+
66+
@Test
67+
void testPeekFrontAfterRemovals() {
68+
queue.insert(1);
69+
queue.insert(2);
70+
queue.insert(3);
71+
queue.remove();
72+
assertEquals(2, queue.peekFront(), "After removing one element, the front should be the second element");
73+
}
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75+
@Test
76+
void testIsEmptyAfterRemovals() {
77+
queue.insert(1);
78+
queue.insert(2);
79+
queue.remove();
80+
queue.remove();
81+
assertTrue(queue.isEmpty(), "Queue should be empty after removing all elements");
82+
}
83+
84+
@Test
85+
void testRemoveFromEmptyQueue() {
86+
org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::remove, "Removing from an empty queue should throw an exception");
87+
}
88+
89+
@Test
90+
void testPeekFrontFromEmptyQueue() {
91+
org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::peekFront, "Peeking front from an empty queue should throw an exception");
92+
}
93+
94+
@Test
95+
void testPeekBackFromEmptyQueue() {
96+
org.junit.jupiter.api.Assertions.assertThrows(EmptyStackException.class, queue::peekBack, "Peeking back from an empty queue should throw an exception");
97+
}
98+
99+
@Test
100+
void testIsInStackEmptyInitially() {
101+
assertTrue(queue.isInStackEmpty(), "inStack should be empty initially");
102+
}
103+
104+
@Test
105+
void testIsOutStackEmptyInitially() {
106+
assertTrue(queue.isOutStackEmpty(), "outStack should be empty initially");
107+
}
108+
109+
@Test
110+
void testIsInStackEmptyAfterInsertion() {
111+
queue.insert(1);
112+
assertFalse(queue.isInStackEmpty(), "inStack should not be empty after an insertion");
113+
}
114+
115+
@Test
116+
void testIsOutStackEmptyAfterInsertion() {
117+
queue.insert(1);
118+
assertTrue(queue.isOutStackEmpty(), "outStack should still be empty after an insertion");
119+
}
120+
121+
@Test
122+
void testIsOutStackEmptyAfterRemoval() {
123+
queue.insert(1);
124+
queue.remove();
125+
assertTrue(queue.isOutStackEmpty(), "outStack should be empty after removing the only element");
126+
}
127+
128+
@Test
129+
void testIsInStackEmptyAfterMultipleRemovals() {
130+
queue.insert(1);
131+
queue.insert(2);
132+
queue.remove();
133+
queue.remove();
134+
assertTrue(queue.isInStackEmpty(), "inStack should be empty after removing all elements");
135+
}
136+
137+
@Test
138+
void testIsOutStackEmptyAfterMultipleRemovals() {
139+
queue.insert(1);
140+
queue.insert(2);
141+
queue.remove();
142+
queue.remove();
143+
assertTrue(queue.isOutStackEmpty(), "outStack should be empty after removing all elements");
144+
}
145+
}

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