Implemented Doubly LinkedList.

Author: Navjinder Virdee

DoublyLinkedList/DoublyLinkedList/DoublyLinkedList.java

@@ -0,0 +1,168 @@
+//Program to Implement DoubleLinkedList.
+
+public class DoublyLinkedList{
+	static class Node{
+		int key;   //data value
+		Node next; //points to next element in the list.
+		Node prev; //points to previous element in the list.
+		
+		public Node(int data){
+			this.key=data;
+			this.next=null;
+			this.prev=null;
+		}
+	}
+	
+	static Node head;  //head of the list i.e first element
+	static Node tail;  //tail of the list i.e last element
+	static int size;   //number of elements in the list.
+
+	public DoublyLinkedList(){
+		head=null;
+		tail=null;
+		size=0;		
+	}
+
+	//function to add elements at the front of the list.
+	public static void pushFront(int number){
+		System.out.println("Inserting data at front : " + number);
+		Node node = new Node(number);
+		if(head==null){
+			head=node;
+			tail=node;
+			size++;
+			return;
+		}
+
+		node.next=head;
+		head.prev=node;
+		head=node;
+		size++;
+	}
+
+	//function to add elements at the back of the list.
+	public static void pushBack(int number){
+		System.out.println("Inserting data at back  : " + number);
+		Node node =new Node(number);
+		if(head==null){
+			head=node;
+			tail=node;
+			size++;
+			return;
+		}
+		
+		Node temp=head;
+		while(temp.next!=null){
+			temp=temp.next;
+		}
+		temp.next=node;
+		node.prev=temp;
+		tail=node;
+		size++;
+	}
+
+	//function to remove element from the front of list.
+	public static void popFront(){
+		System.out.println("PopFront Operation.");
+		if(head==null){
+			System.out.println("Empty List.");
+			return;
+		}
+		if(head.next==null){
+			head=null;
+			tail=null;
+			size--;
+			return;
+		}
+		head=head.next;
+		head.prev=null;
+		size--;
+	}
+	
+	//function to remove elements from the back of the list.
+	public static void popBack(){
+		System.out.println("PopBack Operation.");
+		if(head==null){
+			System.out.println("Empty List.");
+			return;
+		}
+
+		if(head.next==null){
+			head=null;
+			tail=null;
+			size--;
+			return;
+		}
+		
+		Node temp=head;
+		while(temp.next.next!=null){
+			temp=temp.next;
+		}
+		temp.next.prev=null;
+		temp.next=null;
+		tail=temp;
+		size--;
+	}
+
+	//function to display the list.
+	public static void displayF(){
+		System.out.print("List : ");
+		if(head==null){
+			System.out.println("Empty List.");
+			return;
+		}
+		Node temp=head;
+		while(temp!=null){
+			System.out.print(temp.key + " ");
+			temp=temp.next;
+		}
+		System.out.println();
+	}
+		
+	public static void displayB(){
+		System.out.print("Reverse List : ");
+		if(head==null && tail==null){
+			System.out.println("Empty List.");
+			return;
+		}
+
+		Node temp=tail;
+		while(temp!=null){
+			System.out.print(temp.key + " ");
+			temp=temp.prev;
+		}
+		System.out.println();
+	}
+	
+	public static void main(String [] args){
+		DoublyLinkedList list = new DoublyLinkedList();
+		list.pushFront(10);
+		list.pushBack(12);
+		list.pushFront(8);
+		list.pushBack(14);
+		list.displayF();
+		list.displayB();
+
+		list.popFront();
+		list.displayF();
+		list.displayB();
+		list.popBack();
+		list.displayF();
+		list.displayB();
+		
+		list.popFront();
+		list.displayB();
+		list.popFront();
+		list.displayF();
+	}
+}
+		
+	
+				
+		
+
+		
+		
+		
+
+ 

DoublyLinkedList/DoublyLinkedListImplementation/DoublyLinkedList.java

@@ -0,0 +1,185 @@
+//Program to implement Doubly Linked List.
+
+public class DoublyLinkedList{
+	Node head;  //head of the list. i.e first element.
+	Node tail;  //tail of the list. i.e last element.
+	int size;   //number of  elements in the list.
+	
+	public DoublyLinkedList(){
+		head=null;
+		tail=null;
+		size=0;
+	}
+
+	//function to add elements at the front of the list.
+	public void pushFront(int data){
+		System.out.println("Inserting data at front : " + data);
+		Node node = new Node(data);
+		if(head==null && tail==null){
+			head=node;
+			tail=node;
+			size++;
+			return;
+		}
+		
+		node.next=head;
+		head.prev=node;
+		head=node;
+		size++;
+	}
+
+	//function to add elements at the back of the list.
+	public void pushBack(int data){
+		System.out.println("Inserting data at back  : " + data);
+		Node node = new Node(data);
+		if(tail==null && head==null){
+			head=node;
+			tail=node;
+			size++;
+			return;
+		}
+
+		tail.next=node;
+		node.prev=tail;
+		tail=node;
+		size++;
+	}
+
+	//function to remove elements from the front of the list.
+	public void popFront() throws Exception{
+		System.out.println("PopFront Operation.");
+		if(head==null && tail==null){
+			throw new Exception("List is empty!");
+		}
+		if(head==tail){
+			head=null;
+			tail=null;
+			size--;
+			return;
+		}
+		
+		head.next.prev=null;
+		head=head.next;
+		size--;
+	}
+
+	//function to remove elements from the back of the list.
+	public void popBack() throws Exception{
+		System.out.println("PopBack Operation.");
+		if(head==null && tail==null){
+			throw new Exception("List is empty!");
+		}
+		if(head==tail){
+			head=null;
+			tail=null;
+			size--;
+			return;
+		}
+		tail.prev.next=null;
+		tail=tail.prev;
+		size--;
+	}
+	
+	//function to get the first element of the list.
+	public int topFront() throws Exception{
+		if(head==null){
+			throw new Exception("List is empty!");
+		}
+		return head.key;
+	}
+
+	//function to get last element of the list.
+	public int topBack() throws Exception{
+		if(tail==null){
+			throw new Exception("List is empty!");
+		}
+		return tail.key;
+	}
+
+	//function to find specific element in the list.
+	public boolean Find(int data){
+		Node temp=head;
+		while(temp!=null){
+			if(temp.key==data){
+				return true;
+			}
+			temp=temp.next;
+		}
+		return false;
+	}
+	
+	//function to get size of the list.
+	public int size(){
+		return size;
+	}
+
+	//function to display the list.
+	public void forwardDisplay() throws Exception{
+		System.out.print("List : ");
+		Node temp = head;
+		if(temp==null){
+			throw new Exception("List is empty!");
+		}
+		while(temp!=null){
+			System.out.print(temp.key + " ");
+			temp=temp.next;
+		}
+		System.out.println();
+	}
+
+	//function to display the list in reverse direction.
+	public void reverseDisplay() throws Exception{
+		System.out.print("Reverse List : ");
+		Node temp = tail;
+		if(temp==null){
+			throw new Exception("List is empty!");
+		}
+		while(temp!=null){
+			System.out.print(temp.key + " ");
+			temp=temp.prev;
+		}
+		System.out.println();
+	}
+
+	//function to remove specific element from the list.
+	public void remove(int data) throws Exception{
+		System.out.println("Remove data : " + data);
+		Node temp = head;
+		Node prevNode = null;
+		if(temp==null){
+			throw new Exception("List is empty!");
+		}
+		size--;
+ 		
+		if(temp==tail){
+			if(temp.key==data){
+				head=null;
+				tail=null;
+				return;
+			}
+			else{
+				throw new Exception("Data not found");
+			}
+		}
+		if(head.key==data){
+			head=head.next;
+			head.prev=null;
+			return;
+		}
+		while(temp!=null && temp.key!=data){
+			prevNode=temp;
+			temp=temp.next;
+		}
+		prevNode.next=prevNode.next.next;
+		prevNode.next.prev=prevNode;
+		temp=null;
+	}
+}
+
+	
+		
+		
+
+		
+			
+