doubly linked list.cpp

#include<bits/stdc++.h>
using namespace std;
struct node
{
    int data;
    struct node *pre,*next;
};

struct node *head=NULL,*temp,*cur,*pre,*last;

void insert(int v)
{
    pre=head;
    cur=head->next;
    struct node *newnode;
    newnode= (struct node*)malloc(sizeof(struct node));
    cout<<"Enter information for newnode"<<endl;
    cin>>newnode->data;
    newnode->next=NULL;
    newnode->pre=NULL;

    if(pre->data==v)
    {
        newnode->next=pre;
        pre->pre=newnode;
        head=newnode;
    }
    else
    {
        while(cur->data!=v && cur->next!=NULL)
        {
            pre=cur;
            cur=cur->next;
        }
        if(cur->data==v)
        {
            newnode->next=cur;
            cur->pre=newnode;
            pre->next=newnode;
            newnode->pre=pre;
        }
        if(cur->data!=v && cur->next==NULL)
        {
            cout<<"Sorry!! Not found"<<endl;
        }
    }
}

void deletedata(int v)
{
    pre=head;
    cur=head->next;
    if(pre->data==v)
    {
        cur->pre=NULL;
        head=cur;
        delete(pre);
    }
    else
    {
        while(cur->data!=v && cur->next!=NULL)
        {
            pre=cur;
            cur=cur->next;
        }
        if(cur->data==v && cur->next!=NULL)
        {
            cur->next->pre=pre;
            pre->next=cur->next;
            delete(cur);
        }
        if(cur->data==v && cur->next==NULL)
        {
            pre->next=NULL;
            delete(cur);
        }
        else
        {
            cout<<"OPPS!! Not found"<<endl;
        }
    }
}

void display()
{
    temp=head;

    while(temp!=NULL)
    {
        cout<<temp->data<<endl;
        temp=temp->next;
    }
}

void revdisplay()
{
    temp=last;
    while(temp!=NULL)
    {
        cout<<temp->data<<endl;
        temp=temp->pre;
    }
}

int main()
{
    cout<<"Enter how many node you want"<<endl;
    int n;
    cin>>n;
    struct node *s;
    s= (struct node*)malloc(sizeof(struct node));
    for(int i=1; i<=n; i++)
    {
        struct node *newnode;
        newnode= (struct node*)malloc(sizeof(struct node));

        cin>>newnode->data;
        newnode->next=NULL;
        newnode->pre=NULL;

        if(head==NULL)
        {
            head=newnode;
            s=head;
            last=head;
        }
        else
        {
            s->next=newnode;
            newnode->pre=s;
            newnode->next=NULL;
            s=newnode;
            last=newnode;
        }
    }
    cout<<endl;

    display();
    cout<<endl;
    revdisplay();

    int v;
    cout<<"Enter a data where u want to insert"<<endl;
    cin>>v;

    insert(v);

    cout<<endl;
    display();

    cout<<"Enter a data which you want to delete"<<endl;
    cin>>v;

    deletedata(v);

    cout<<endl;
    display();
    return 0;
}