Question

(Data Strcture)

Tool(s)/Software Java programming language with NetBeans IDE. Description Implementing a Linear Queue using a Singly Linked-List and Implementing a Priority Queue Tasks/Assignments(s) ■ Write your own program to implement priority queue using the Linked-List and implement the Enqueue, Dequeue and Display methods. implement the Merge methods in your main program that receive Q1 and Q2 and merge the two queues into one queue. Public static PriorityQueue MergeQueue(PriorityQueue Q1,PriorityQueue Q2) Write main program to test priority queue class and apply the following test case:

Answer 1

Priority Queue using Linked List

// Java code to implement Priority Queue
// using Linked List
import java.util.* ;

class Solution
{
  
  
// Node
static class Node {
   int data;
  
   // Lower values indicate higher priority
   int priority;
  
   Node next;
  
}

static Node node = new Node();
  
// Function to Create A New Node
static Node newNode(int d, int p)
{
   Node temp = new Node();
   temp.data = d;
   temp.priority = p;
   temp.next = null;
  
   return temp;
}
  
// Return the value at head
static int peek(Node head)
{
   return (head).data;
}
  
// Removes the element with the
// highest priority form the list
static Node pop(Node head)
{
   Node temp = head;
   (head) = (head).next;
   return head;
}
  
// Function to push according to priority
static Node push(Node head, int d, int p)
{
   Node start = (head);
  
   // Create new Node
   Node temp = newNode(d, p);
  
   // Special Case: The head of list has lesser
   // priority than new node. So insert new
   // node before head node and change head node.
   if ((head).priority > p) {
  
       // Insert New Node before head
       temp.next = head;
       (head) = temp;
   }
   else {
  
       // Traverse the list and find a
       // position to insert new node
       while (start.next != null &&
           start.next.priority < p) {
           start = start.next;
       }
  
       // Either at the ends of the list
       // or at required position
       temp.next = start.next;
       start.next = temp;
   }
   return head;
}
  
// Function to check is list is empty
static int isEmpty(Node head)
{
   return ((head) == null)?1:0;
}
  
// Driver code
public static void main(String args[])
{
   // Create a Priority Queue
   // 7.4.5.6
   Node pq = newNode(4, 1);
   pq =push(pq, 5, 2);
   pq =push(pq, 6, 3);
   pq =push(pq, 7, 0);
  
   while (isEmpty(pq)==0) {
       System.out.printf("%d ", peek(pq));
       pq=pop(pq);
   }
  
}
}

Output:
7 4 5 6

Methods for enqueue and dequeue:

// Method to add an key to the queue.   
void enqueue(int key)
{
  
// Create a new LL node
QNode temp = new QNode(key);

// If queue is empty, then new node is front and rear both
if (this.rear == null)
{
this.front = this.rear = temp;
return;
}

// Add the new node at the end of queue and change rear
this.rear.next = temp;
this.rear = temp;
}

// Method to remove an key from queue.   
QNode dequeue()
{
// If queue is empty, return NULL.
if (this.front == null)
return null;

// Store previous front and move front one node ahead
QNode temp = this.front;
this.front = this.front.next;
// If front becomes NULL, then change rear also as NULL
if (this.front == null)
this.rear = null;
return temp;
}

static class ArrayQmerge{
private List<Integer> queue = new ArrayList<Integer>();

public void enqueue(int val){
queue.add(val);
}

public String toString(){
return queue.toString();
}

public void mergeQs(ArrayQmerge q){
List<Integer> mergedQ = new ArrayList<Integer>(this.queue.size() + q.queue.size());
for (int i = 0, j = 0; i < this.queue.size() || j < q.queue.size();){
if (i < this.queue.size())
mergedQ.add(this.queue.get(i++));
if (j < q.queue.size())
mergedQ.add(q.queue.get(j++));
}
this.queue = mergedQ;
}
}

Priority Queue class

public static void main(String[] args) {
PriorityQueue Q1 = new PriorityQueue();
Q1.enqueue(1,Mohammed);
Q1.enqueue(3,"Fahd");
Q1.enqueue(8,"Khaled");
Q1.enqueue(9,"Osama");
Q1.enqueue(5,"Mostafa");
PriorityQueue Q2 = new PriorityQueue();
Q2.enqueue(2,"Hany");
Q2.enqueue(5,"Mostafa");
Q2.enqueue(9,"Osama");
Q2.enqueue(10,"Marwan");
Q2.enqueue(6,"Hazem");
System.out.println(Q1);
System.out.println(Q2);
Q1.mergeQs(Q2);
System.out.println(Q1);
System.out.println(Q2);
}

static class PriorityQueue{
private List<Integer> queue = new ArrayList<Integer>();

public void enqueue(int val){
queue.add(val);
}

public String toString(){
return queue.toString();
}

public void mergeQs(PriorityQueue q){
List<Integer> mergedQ = new ArrayList<Integer>(this.queue.size() + q.queue.size());
for (int i = 0, j = 0; i < this.queue.size() || j < q.queue.size();){
if (i < this.queue.size())
mergedQ.add(this.queue.get(i++));
if (j < q.queue.size())
mergedQ.add(q.queue.get(j++));
}
this.queue = mergedQ;
}
}