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GauravWalia19GauravWalia19
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added priority queue using array in java
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‎Java/Data-Structures/QUEUES/PRIORITY-QUEUE/ArrayPriorQueue.java

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import java.util.*;
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abstract class ArrayPriorQueue
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{
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// class for creating QueueOverflow exception
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private static class QueueOverflowException extends Exception
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{
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private static final long serialVersionUID = 1L;
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public QueueOverflowException(String message)
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{
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super(message);
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}
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public String toString()
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{
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return "myjava.QueueOverflowException: "+getMessage();
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}
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}
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//class for creating Empty Queue exception
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private static class EmptyQueueException extends Exception
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{
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private static final long serialVersionUID = 1L;
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public EmptyQueueException(String str)
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{
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super(str);
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}
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public String toString()
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{
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return "myjava.EmptyQueueException: "+getMessage();
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}
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}
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// Node class for storing data with priorities
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private static class Node
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{
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private int priority; // priority of data
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private int data; // data in the node
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public Node(int data,int priority) // constructor
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{
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this.data=data;
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this.priority = priority;
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}
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/**
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* It will return the priority of the node
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*
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* @return int for priority
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**/
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public int getPriority()
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{
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return priority;
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}
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/**
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* It will return the data of the node
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*
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* @return int for data
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**/
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public int getData()
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{
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return data;
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}
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}
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// class for priority queue
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private static class PriorQueue
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{
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private Node[] arr; // array for queue
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private int capacity; // for setting capacity of the queue
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private int front; // front index of the queue
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private int rear; // rear index of the queue
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/**
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* Valued Constructor for making queue with the given capacity
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*
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* @param int for capacity
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**/
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public PriorQueue(int capacity)
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{
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this.capacity = capacity;
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arr = new Node[capacity];
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front=-1;
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rear=-1;
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}
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/**
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* Default Constructor for making the queue with default size i.e 10
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**/
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public PriorQueue()
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{
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this(10);
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}
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/**
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* This function will add one element to the queue according to the priority
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*
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* @param int for data
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* @param int for priority
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* @exception QueueOverflowException
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**/
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public void enqueue(int data,int priority) throws QueueOverflowException
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{
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if(rear+1==capacity)
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{
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throw new QueueOverflowException("Queue Overflow !!!");
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}
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Node newNode = new Node(data,priority);
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if(rear==-1 && front==-1)
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{
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front++;
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rear++;
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arr[rear] = newNode;
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}
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else if(priority <= arr[0].getPriority()) //search for correct position in the array according to priority
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{
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//shift the array
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rear++;
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for(int i=rear;i>0;i--)
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{
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arr[i] = arr[i-1];
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}
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arr[0] = newNode; // insert at front
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}
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else if(priority >= arr[rear].getPriority()) // insert at last
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{
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rear++;
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arr[rear] = newNode;
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}
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else // insert in between
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{
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//search position in the array for insertion
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int i=-1;
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for(i=0;i<=rear;i++)
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{
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if(priority <= arr[i].getPriority())
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{
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break;
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}
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}
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rear++;
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for(int j=rear;j>i;j--) // shift half right array to right
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{
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arr[j] = arr[j-1];
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}
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arr[i] = newNode; // insert the node
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}
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}
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/**
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* This function will remove an element from priority queue
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*
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* @return int for returning the removed element
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* @exception EmptyQueueException
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**/
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public int dequeue() throws EmptyQueueException
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{
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if(front==-1 || rear==-1)
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{
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throw new EmptyQueueException("Empty Queue !!!");
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}
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int result = arr[front].getData();
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for(int i=0;i<rear;i++)
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{
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arr[i] = arr[i+1];
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}
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rear--;
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return result;
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}
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/**
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* This function will only return the front element of priority queue
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*
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* @return int for front element
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* @exception EmptyQueueException
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**/
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public int peek() throws EmptyQueueException
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{
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if(front==-1 || rear==-1)
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{
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throw new EmptyQueueException("Empty Queue !!!");
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}
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return arr[front].getData();
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}
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/**
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* This function will print the queue
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**/
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public void print()
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{
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for(int i=front;i<=rear;i++)
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{
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System.out.println(arr[i].getPriority() + " " + arr[i].getData());
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}
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}
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}
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public static void main(String[] args)
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{
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try
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{
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PriorQueue Q = new PriorQueue();
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Q.enqueue(12, 1);
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Q.enqueue(31, 1);
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Q.enqueue(13, 0);
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Q.enqueue(24, 4);
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Q.enqueue(34, 8);
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Q.enqueue(100, 3);
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Q.enqueue(200, 3);
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Q.enqueue(120, 0);
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Q.enqueue(202, 5);
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Q.enqueue(223, 9);
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// Q.enqueue(2323, 0);
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Q.print();
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.dequeue());
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System.out.println(Q.peek());
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}
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catch(Exception e)
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{
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System.out.println(e);
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}
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}
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}

‎Java/README.md

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* FIXED ARRAY CIRCULAR QUEUE
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* LINKED CIRCULAR QUEUE
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* PRIORITY QUEUE
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* FIXED ARRAY PRIORITY QUEUE
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* [FIXED ARRAY PRIORITY QUEUE](Data-Structures/QUEUES/PRIORITY-QUEUE/ArrayPriorQueue.java)
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* LINKED PRIORITY QUEUE
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* HEAPED PRIORITY QUEUE
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* MISC QUEUE

‎datastructures.md

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* blog
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* docs
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* implementation
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* complexity
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* [JAVA](Java/Data-Structures/QUEUES/PRIORITY-QUEUE/ArrayPriorQueue.java)
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* [complexity](docs/complexity.md#fixed-array-priority-queue)
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#### LINKED PRIORITY QUEUE
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‎docs/complexity.md

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##### FIXED ARRAY PRIORITY QUEUE
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SNo. | Operations | Order and Type of Time Complexity O(n) | Order and Type of Space Complexity
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---- | ---------- | -------------------------------------- | ----------------------------------
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1 | Insert element with priority | O(n) -- Linear | O(1) -- Constant
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2 | Delete element with highest priority | O(n) -- Constant | O(1) -- Constant
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3 | Print the queue | O(n) -- Linear | O(1) -- Constant
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4 | Size of the queue | O(1) -- Constant | O(1) -- Constant
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5 | Queue is Empty or not | O(1) -- Constant | O(1) -- Constant
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##### LINKED PRIORITY QUEUE
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SNo. | Operations | Order and Type of Time Complexity O(n) | Order and Type of Space Complexity

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