Doubly linked list in C++

Author: Deepali-Srivastava

linked-list/doubly-linked-list/DoublyList.cpp

@@ -0,0 +1,327 @@
+/*
+Copyright (C) Deepali Srivastava - All Rights Reserved
+This code is part of DSA course available on CourseGalaxy.com    
+*/
+
+
+/*Doubly linked list*/
+
+#include<iostream>
+#include "Node.h"
+#include "Doubly.h"
+
+using namespace std;
+
+DoublyLinkedList::DoublyLinkedList() 
+{
+	start = NULL;
+}
+
+DoublyLinkedList::DoublyLinkedList(const DoublyLinkedList& L)
+{
+	if( L.start == NULL )
+	{
+		start = NULL;
+		return;
+	}		
+	Node *p1,*p2, *previous;
+		
+	p1 = L.start;
+	p2 = start = new Node(p1->info);
+	previous = NULL;
+	
+	p1 = p1->next;
+
+	while( p1 != NULL )
+	{		
+		p2->next = new Node(p1->info);
+		p2->prev = previous;
+		previous = p2;
+		p2 = p2->next;
+		p1 = p1->next;
+	}
+	p2->prev = previous;
+}
+
+DoublyLinkedList::~DoublyLinkedList()
+{
+	Node *p;
+	while( start != NULL )
+	{
+		p = start->next;
+		delete start;
+		start = p;
+	}
+}
+
+inline bool DoublyLinkedList::isEmpty() const
+{
+	return start == NULL;
+}
+
+void DoublyLinkedList::displayList() const
+{
+	Node *p;
+	if(isEmpty())
+	{
+		cout<<"List is empty\n";
+		return;
+	}
+	p = start;
+	cout<<"List is :\n";
+	while( p != NULL )
+	{
+		cout << p->info << "  ";
+		p = p->next;
+	}
+	cout<<"\n";
+}
+
+inline void DoublyLinkedList::insertInEmptyList(int data)
+{
+	Node *temp = new Node(data);
+	start = temp;
+}
+
+void DoublyLinkedList::insertAtBeginning(int data)
+{
+	if(isEmpty())
+	{
+		insertInEmptyList(data);
+		return;
+	}
+	Node *temp = new Node(data);
+	temp->next = start;
+	start->prev = temp;
+	start = temp;
+}
+
+void DoublyLinkedList::insertAtEnd(int data)
+{
+	if(isEmpty())
+	{
+		insertInEmptyList(data);
+		return;
+	}
+	
+	Node *temp = new Node(data);
+	
+	Node *p = start;
+	while( p->next != NULL )
+		p = p->next;	
+	
+	p->next = temp;
+	temp->prev = p;
+}
+
+void DoublyLinkedList::createList()
+{
+	int i,n,data;
+	
+	cout << "Enter the number of nodes : ";
+	cin >> n;
+	
+	if( n <= 0 )
+		return;
+
+	cout << "Enter the first element to be inserted : ";
+	cin >> data;
+	insertInEmptyList(data);
+	
+	Node *p = start;
+	for( i=2; i<=n; i++ )
+	{
+		cout << "Enter the next element to be inserted : ";
+		cin >> data;
+		Node *temp = new Node(data);
+	    
+	    p->next = temp;
+	    temp->prev = p;
+		p = temp;
+	}
+}
+
+void DoublyLinkedList::insertAfter(int data, int x)
+{
+	Node *temp = new Node(data);
+
+	Node *p = start;
+	while( p != NULL )
+	{
+		if( p->info == x )
+			break;
+		p = p->next;
+	}
+	if(p == NULL)
+		cout << x << " not present in the list\n\n";
+	else
+	{
+		temp->prev = p;
+		temp->next = p->next;
+		if( p->next != NULL ) 
+			p->next->prev = temp; //should not be done when p points to last node
+		p->next = temp;
+	}
+}
+	
+void DoublyLinkedList::insertBefore(int data,int x)
+{
+	Node *temp;
+	if( isEmpty() )
+	{
+		cout<<"List is empty\n";
+		return;
+	}
+	if( start->info == x )  // x is in first node 
+	{
+		insertAtBeginning(data);
+		return;
+	}
+	Node *p = start;
+	while( p != NULL )
+	{
+		if( p->info == x )
+			break;
+		p = p->next;
+	}	
+	
+	if ( p == NULL )
+		cout << x << "not present in the list\n";		
+	else
+	{
+		temp = new Node(data);
+		temp->prev = p->prev;
+		temp->next = p;
+		p->prev->next = temp;
+		p->prev = temp;
+	}	
+}
+
+void DoublyLinkedList::deleteFirstNode()
+{
+	if( isEmpty() )
+	{
+		cout<<"List is empty\n";
+		return;
+	}
+   
+	Node *temp = start;
+	if (start->next == NULL) // list has only one node
+		start = NULL;
+	else
+	{
+		start = start->next;
+        start->prev = NULL;
+	}
+	delete temp;
+}
+ 
+void DoublyLinkedList::deleteLastNode()
+{
+	if( isEmpty() )
+	{
+		cout<<"List is empty\n";
+		return;
+	}
+	
+	Node *temp;
+
+    if( start->next == NULL )  // list has only one node
+    {       
+		temp = start;
+		start = NULL;  
+    }
+	else
+	{
+		temp = start;
+		while( temp->next != NULL )
+			temp = temp->next;
+		temp->prev->next = NULL;
+	}
+	delete temp;
+}
+
+void DoublyLinkedList::deleteNode(int x)
+{
+	if(isEmpty())
+	{
+		cout<<"List is empty\n";
+		return;
+	}
+
+	Node *temp;
+	if( start->next == NULL )	/*only one node in the list*/
+		if( start->info == x ) 
+		{
+			temp = start;
+			start = NULL;
+			delete temp;
+			return;
+		}
+		else
+		{
+			cout<<"Element "<< x <<" not found\n";
+			return;
+		}
+	/*Deletion of first node*/
+	if( start->info == x )
+	{
+		temp = start;
+		start = start->next;  
+		start->prev = NULL;
+		delete temp;
+		return;
+	}
+	
+	temp = start->next;
+	while( temp->next != NULL )
+	{
+		if( temp->info == x )     
+			break;
+		temp = temp->next;
+	}
+	
+	if( temp->next != NULL )
+	{
+		temp->prev->next = temp->next;
+		temp->next->prev = temp->prev;
+		delete temp;
+	}
+	else
+	{
+		if( temp->info == x ) //node to be deleted is last node
+		{
+			temp->prev->next = NULL;
+			delete temp;
+		}
+        else
+			cout << x << "not found\n";
+	}
+}
+
+	
+void DoublyLinkedList::reverseList()
+{	
+	if( isEmpty() )
+	{
+		cout<<"List is empty\n";
+		return;
+	}	
+	
+	Node *p = start;
+	Node *temp;
+	while( p->next != NULL )
+	{
+		temp = p->next;
+		p->next = p->prev;
+		p->prev = temp;
+		p = p->prev;
+	}
+	p->next = p->prev;
+	p->prev = NULL;
+	start = p;
+}
+
+
+
+