Doubly Linked List (Data Structure) In C++

A doubly-linked list is a linked data structure that consists of a set of sequentially linked records called nodes. Each node contains two fields, called links, that are references to the previous and to the next node in the sequence of nodes.#include “stdio.h”
#include “conio.h”
#include “iostream.h”
using namespace std;
int insertdata(int x);
void display();
void deleteint(int x);
void reversel();
int searchint(int x);
int compare_fn(int a,int b)
{
if(a>b)
return 1;
else if(b>a)
return -1;
}
int compare_no=1;
struct node
{
int data;
node *prev;
node *next;
};
node *top = NULL;
int main()
{
int ch,d,y;
char ans=’y’;
while(ans==’y’)
{
cout<<“nt 1.Insert 2. Delete 3.Reverse 4.EXITnEnter Choice : “;
cin>>ch;
if(ch==1)
{
cout<<“Enter An Element To be inserted : “;
cin>>d;
d=insertdata(d);
display();
}
else if(ch==2)
{
cout<<“Enter Element To Be Deleted : “;
cin>>d;
deleteint(d);
display();
}
else if(ch==3)
reversel();
else
return 0;
}
return 0;
}
int searchint(int x)
{
int count=0;
node *searchele=top;
while( searchele!=NULL)
{
if(compare_fn(x,searchele->data)==compare_no)
{
searchele=searchele->next;
count+=1;
}
else
break;
}
return count;
}
int insertdata(int x)
{
if(top==NULL)
{
top=new node;
top->data=x;
top->next=NULL;
top->prev=NULL;
}
else if(compare_fn(top->data ,x)==compare_no)
{
node *n=new node;
n->data=x;
n->next=top;
n->prev=NULL;
top->prev=n;
top=n;
}
else
{
int c=searchint(x);
node *insertele=top;
for(int i=0;i<c-1;i++)
insertele=insertele->next;
node *n=new node;
n->data=x;
node *b=insertele->next;
node *N =insertele;
n->prev=insertele;
n->next=b;
insertele->next=n;
if(b!=NULL)
b->prev=n;
}
}
void display()
{
cout<<“Element In The Linked List Are : “;
node *disp=top;
while(disp!=NULL)
{
cout<<” “<<disp->data;
if(disp->next==NULL)
{
break;
}
disp=disp->next;
}
}
void deleteint(int x)
{
node *del=top;
if(del->data == x)
{
if(del->next==NULL && del->prev==NULL)
{
top=NULL;
return;
}
del->next->prev=NULL;
top=del->next;
}
else
{
node *delsuc=del->next;
if(del==NULL)
{
cout<<“nElement Not Foundn”;
return;
}
if(delsuc==NULL)
{
cout<<“nElement Not Foundn”;
return;
}
while(delsuc->data != x)
{
del=del->next;
delsuc=delsuc->next;
if(del==NULL)
{
cout<<“nElement Not Foundn”;
return;
}
if(delsuc==NULL)
{
cout<<“nElement Not Foundn”;
return;
}
}
del->next=delsuc->next;
if(delsuc->next!=NULL)
delsuc->next->prev=del;
}
}
void reversel()
{
node *a=top;
node *b,*c,*d;
while(a!=NULL)
{
d=a;
c=a->next;
b=a->prev;
a->prev=a->next;
a->next=b;
a=c;
}
top=d;
cout<<“After Reversing the linked list”;
display();
compare_no*=-1;
}This is a doubly linked list program in C++. Each Node will have a reference pointer to its next as well as previous node.It maintains an ascending order. So new elements are inserted in the right place.Reversing A Linked List will reverse the list as well as the property Ascending becomes descending and vice-versa. So Order of various Process :Insertion : O(n)Deletion : O(n)Reversal : O(n)Search : O(n)

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