Code:
import java.util.*;
/* Class queueUsingStack */
class queueUsingStack
{
Stack
Stack
/* Constructor */
public queueUsingStack()
{
s = new Stack
tmp = new Stack
}
/* Function to insert an element to the queue */
public void insert(int data)
{
/* if no element is present in stack s then
* push the new element to stack s */
if (s.size() == 0)
s.push(data);
else
{
/* if elements are present in stack s then
* pop all the elements from stack s and
* push them to stack tmp */
int l = s.size();
for (int i = 0; i < l; i++)
tmp.push(s.pop());
/* push the new element to stack s */
s.push(data);
/* pop all elements from stack tmp and
* push them to stack s */
for (int i = 0; i < l; i++)
s.push(tmp.pop());
}
}
/* Function to remove front element from the queue */
public int remove()
{
if (s.size() == 0)
throw new NoSuchElementException("Underflow Exception");
return s.pop();
}
/* Function to check the front element of the queue */
public int peek()
{
if (s.size() == 0)
throw new NoSuchElementException("Underflow Exception");
return s.peek();
}
/* Function to check if queue is empty */
public boolean isEmpty()
{
return s.size() == 0 ;
}
/* Function to get the size of the queue */
public int getSize()
{
return s.size();
}
/* Function to display the status of the queue */
public void display()
{
System.out.print("\nQueue = ");
int l = getSize();
if (l == 0)
System.out.print("Empty\n");
else
{
/* Iterator wont return for stack in order */
for (int i = l - 1; i >= 0; i--)
System.out.print(s.get(i)+" ");
System.out.println();
}
}
}
/* Class QueueImplementUsingTwoStacks */
public class QueueImplementUsingTwoStacks
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
/* Creating object of class queueUsingStack */
queueUsingStack qus = new queueUsingStack();
/* Perform Queue Operations */
System.out.println("Queue Using Two Stacks Test\n");
char ch;
do
{
System.out.println("\nQueue Operations");
System.out.println("1. insert");
System.out.println("2. remove");
System.out.println("3. peek");
System.out.println("4. check empty");
System.out.println("5. size");
int choice = scan.nextInt();
switch (choice)
{
case 1 :
System.out.println("Enter integer element to insert");
qus.insert( scan.nextInt() );
break;
case 2 :
try
{
System.out.println("Removed Element = "+ qus.remove() );
}
catch (Exception e)
{
System.out.println("Error : " + e.getMessage());
}
break;
case 3 :
try
{
System.out.println("Peek Element = "+ qus.peek() );
}
catch (Exception e)
{
System.out.println("Error : " + e.getMessage());
}
break;
case 4 :
System.out.println("Empty status = "+ qus.isEmpty() );
break;
case 5 :
System.out.println("Size = "+ qus.getSize() );
break;
default :
System.out.println("Wrong Entry \n ");
break;
}
/* Display Queue */
qus.display();
System.out.println("\nDo you want to continue (Type y or n) \n");
ch = scan.next().charAt(0);
} while (ch == 'Y'|| ch == 'y');
}
}
Output:
Queue Using Two Stacks Test
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
4
Empty status = true
Queue = Empty
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
99
Queue = 99
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
162
Queue = 99 162
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
3
Queue = 99 162 3
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
77
Queue = 99 162 3 77
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
42
Queue = 99 162 3 77 42
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
67
Queue = 99 162 3 77 42 67
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
1
Enter integer element to insert
34
Queue = 99 162 3 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
5
Size = 7
Queue = 99 162 3 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
3
Peek Element = 99
Queue = 99 162 3 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 99
Queue = 162 3 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 162
Queue = 3 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 3
Queue = 77 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 77
Queue = 42 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 42
Queue = 67 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 67
Queue = 34
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
2
Removed Element = 34
Queue = Empty
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
3
Error : Underflow Exception
Queue = Empty
Do you want to continue (Type y or n)
y
Queue Operations
1. insert
2. remove
3. peek
4. check empty
5. size
5
Size = 0
Queue = Empty
Do you want to continue (Type y or n)
n
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