Doubly Linked List Implementation

Following program gives Implementation of Doubly Linked List with its various operations:

/************************************************************* * Author: Aniruddha S N * */ #include<iostream> using namespace std; // structure node struct node { int info; struct node* next; struct node* prev; }; //function declarations void display_list(); void Insert_Element_List(int ele); void DeleteElementAtPos(int pos); void display_Prev_Next(int pos); void delete_Entire_list(); //global variable first node* first = NULL; //main function int main() { int ele = 0; int ch = 0; int pos = 0; //Menu to display Doubly linked list operations while(1) { cout<<"**************DoublyLinkedListOperationsMenu*************\n"; cout<<"1---->Insert an element in list\n"; cout<<"2---->displayList\n"; cout<<"3---->DeleteAnElement at specified position in list\n"; cout<<"4---->Display Previous and Next ele of the mentioned node\n"; cout<<"5---->exit\n"; cout<<"***************************************************\n"; cout<<"\n\n"; cout<<"Enter your choice:\n"; cin>>ch; //using switch case call respective functions for respective choices switch(ch) { case 1: cout<<"Enter the element to be inserted into list\n"; cin>>ele; Insert_Element_List(ele); break; case 2:display_list(); break; case 3:cout<<"Enter the position to delete elements\n"; cin>>pos; DeleteElementAtPos(pos); break; case 4:cout<<"Enter the Node Position to display previous and next ele\n"; cin>>pos; display_Prev_Next(pos); break; default: delete_Entire_list(); exit(0); } } return 0; }//end of main //function to insert an element in singly linked list void Insert_Element_List(int ele) { node* temp; if(first == NULL) { first= new node(); first->info=ele; first->next=NULL; first->prev=NULL; } else { node* temp1; temp1 = new node(); temp=first; //find the end of list while( temp->next != NULL) temp=temp->next; temp1->info=ele; temp1->next=NULL; //attach the new node at the end of list temp->next=temp1; temp1->prev=temp; } } //function to display the elements in the list void display_list() { if ( first == NULL) cout<<"list doesnt have any elements"; else if(first->next == NULL) { cout<<"List Contents:\n"; cout<<first->info<<"\n"; } else { node* temp; temp=first; cout<<"List Contents:\n"; while( temp != NULL) { cout<<temp->info<<"\n"; temp=temp->next; } } } //function to delete element at specified position void DeleteElementAtPos(int pos) { int flag = 0; node* prev; node* temp; if( first == NULL ) { cout<<"List Empty\n"; } else if( pos >1 && first->next == NULL ) { cout<<"No element at specified position in list\n"; } else if( pos ==1) { temp=first; prev=temp; temp=temp->next; temp->prev=NULL; //re initiate first first=temp; prev->next=NULL; prev->prev=NULL; delete prev; prev= NULL; } // for all other positions else { temp=first; flag=1; while(flag < pos && temp->next != NULL) { prev=temp; temp=temp->next; flag++; } //check whether the specified position exists if( flag < pos) { cout<<"No element at specified position in list\n"; } //delete the node at the specified position else { prev->next = temp->next; temp->next->prev=prev; temp->next=NULL; temp->prev=NULL; delete temp; temp=NULL; } }//end of else for all other positions } void display_Prev_Next(int pos) { if(first == NULL) cout<<"List empty\n"; else if(first->next == NULL) cout<<"Only one element in List\n"; //for other valid cases else { node* temp=first; node* prev; int flag=1; while( flag < pos && temp->next!=NULL) { prev=temp; flag++; temp=temp->next; } //check whether its an invalid node position if(flag < pos) { cout<<"No element at specified position in the list\n"; } //if the position is valid else { cout<<"Previous Node:"<<prev->info<<"\n"; cout<<"Current Node:"<<temp->info<<"\n"; if(temp->next == NULL) cout<<"Next Node:End of List\n"; else cout<<"Next Node:"<<temp->next->info<<"\n"; } } //end of else other valid cases } //function to delete entire list and prevent memory leakage when exit is called void delete_Entire_list() { node* temp; node* curr; temp=first; if(first == NULL) return; while(temp->next != NULL) { curr=temp; temp=temp->next; delete curr; } delete temp; }