//**************************************
//
// Name: two-way linked list
// Description:this is the implementatio
// n of two-way linked list in oop technolo
// gy.
if u are using the code for any purpose do favour me and vote for this code .
// By: jetendar dherwani
//
// Inputs:no
//
// Returns:no
//
// Assumes:u must be aware of by values
// passed in the functions by reference . a
// little bit of knowledge of two-way list
//
// Side Effects:no
//
//This code is copyrighted and has// limited warranties.Please see http://
// www.Planet-Source-Code.com/xq/ASP/txtCod
// eId.3320/lngWId.3/qx/vb/scripts/ShowCode
// .htm//for details.//**************************************
//
//this is the implementation of two way
// linked list
//created by jetendar dherwani
//concepts given by sir faheem qureshi
//in simple linked list i.e one way list
// we have only one pointer
//that helps us moving in forward direct
// ion(only forward not backward) .
//this is the biggest flaw in simple lin
// ked list .
//this flaw is covered or u can say remo
// ved in two-way list .
//we have the same clas student through
// which we will perform some experiments
#include <iostream.h>
#include <conio.h>
#include <alloc.h>
#include <stdlib.h>
class student
{
public:
int data;
student *next;//this will help in moving forward
student *previous ; //this will help in moving backward
public :
student(void);
void insert_beg(int);
void insert_end(int,student *&);
void insert_middle(int loc1,int element,student *&);
void insert_byelement(int data,student *&);
void del_beg(void);
void del_end(student *&);
void del_middle(int loc,student *&);
int count();
void traverse(void);
};
void student::del_middle(int loc,student *&end;)
{
student *ptr;
ptr=next;
for(int i=1;i<=loc-1;i++)
ptr=ptr->next;
if(loc==count() )
{
end=ptr->previous;
ptr->previous->next=NULL;
}
else
{
ptr->next->previous=ptr->previous;
ptr->previous->next=ptr->next;
}
}
void student::del_end(student *&final;)
{
final->previous->next=NULL;
final=final->previous->previous;
}
void student ::insert_byelement(int element,student *&end;)
{
student *ptr,*temp;
ptr=next;
while(1)
{
if(ptr->data >= element)
{
temp=new student();
temp->data=element;
temp->next=ptr;
temp->previous=ptr->previous;
(temp->previous)->next=temp;
ptr->previous=temp;
break;
}
else
{
if(ptr->next==NULL)
{
temp=new student();
temp->data=element;
ptr->next=temp;
temp->previous=ptr;
end=ptr->next;
break;
}
}
ptr=ptr->next;
}
}
void student::insert_middle(int loc,int element,student *&end;)
{
student *ptr,*temp;
ptr=next;
for(int i=1;i<=loc-1;i++)
ptr=ptr->next;
if(ptr->next==NULL)
{
temp=new student();
ptr->next=temp;
temp->previous=ptr;
temp->data=element;
end=temp;
}
else
{
temp=new student();
temp->data=element;
temp->next=ptr->next;
temp->previous=ptr;
ptr->next=temp;
temp->next->previous=temp;
}
}
void student::del_beg(void)
{
student *ptr;
ptr=next;
ptr->next->previous=ptr->previous;
next=ptr->next;
}
void student ::insert_end(int element,student *&ending;)
{
student *newptr,*ptr;
ptr=ending;
newptr=new student();
newptr->data=element;
newptr->previous=ptr;
ptr->next=newptr;
ending=newptr;
}
void student::insert_beg(int element)
{
student *ptr,*newptr;
ptr=next;
newptr=new student();
newptr->previous=ptr->previous;
newptr->data=element;
newptr->next=ptr;
next=newptr;
ptr->previous=newptr;
}
student::student(void)
{
data=-1;
next=NULL;
previous=NULL;
}
void student ::traverse(void)
{
student *ptr;
ptr=next;
while(ptr!=NULL)
{
cout<<'\n'<<ptr->data;
ptr=ptr->next;
}
}
int student::count(void)
{
int count=0;
student *ptr;
ptr=next;
while(ptr!=NULL)
{
count=count+1;
ptr=ptr->next;
}
return(count);
}
void main(void)
{
student *start,*end,*list;
//we will need two pointers to point sta
// rting element of the list
//and another to point to ending element
// of the list
//and list is a generator
clrscr();
list=new student();
start=list;
end=list;
list->insert_end(2,end);
list->insert_end(3,end);
list->insert_end(5,end);
list->traverse();
cout<<'\n'<<"THE TOTAL NUMBER OF ELEMENTS ARE "<<start->count();
list->insert_beg(0);
list->traverse();
getch();
list->del_beg();
list->traverse();
getch();
list->insert_middle(3,1,end);
list->traverse();
getch();
list->insert_byelement(1,end);
list->insert_byelement(9,end);
list->traverse();
getch();
cout<<'\n'<<"nnnnn";
getch();
list->del_end(end);
list->traverse();
getch();
list->del_middle(5,end);
list->traverse();
getch();
list->insert_end(9,end);
list->traverse();
}
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