DLL

//dll
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
int val;
struct dll
{
    int info;
    struct dll *next;
    struct dll *prev;
}*node=NULL,*start=NULL,*prev=NULL,*temp=NULL;
void create_node()
{
    node=(struct dll *)malloc(sizeof(struct dll));
    if(node==NULL)
    {
        printf("\n Node is not allocated memory");
        return;

    }
    node->next=NULL;
    node->prev=NULL;
}
void insert_beg();
void insert_end();
void display()
{
    temp=start;
    if(start==NULL)
    {
        printf("\n DLL is empty for DIsplay");
        return;
    }
    printf("\n Displayed DLl");
    while(temp!=NULL)
    {
        printf("\n =>  %d",temp->info);
        temp=temp->next;
    }
}
void insert_beg()
{
    create_node();
    printf("\n Enter the value: ");
    scanf("%d",&val);

    if(start==NULL)
    {
        node->info=val;

        start=node;

    }
    else
    {
        node->info=val;
        node->next=start;
        start->prev=node;
        start=node;
    }
    display();
}
void insert_end()
{
    if(start==NULL)
    {
        insert_beg();
        return;
    }
    create_node();
    temp=start;
    while(temp->next!=NULL)
    {
        temp=temp->next;
    }

    printf("\n Enter the value: ");
    scanf("%d",&val);
    node->info=val;
    node->prev=temp;
    temp->next=node;
    display();
}
void insert_spc_val()
{
    int t=0,l;
    if(start==NULL)
    {
        printf("\n no values for select ");
        return;

    }
    printf("\n select from following dll\n");
    display();
    printf("\n select the the value: ");
    scanf("%d",&val);
    temp=start;
    while(temp!=NULL)
    {
        if(start->info==val)
        {
            insert_beg();
            t=1;
            return;
        }
        if(temp->info==val)
        {
            t=1;
            break;
        }
        prev=temp;
        temp=temp->next;
    }
    if(t==0)
    {
        printf("\n wrong value inserted");
        display();
    }
    else
    {
        create_node();
        printf("\n ENter the value: ");
        scanf("%d",&l);

        node->info=l;
        node->prev=prev;
        node->next=temp;
        prev->next=node;
        temp->prev=node;

        display();
    }
}
void insert_spc_posi()
{
    int t=0;
    if(start==NULL)
    {
        printf("\n no values for select ");
        return;

    }
    printf("\n select from following dll\n");
    display();
    printf("\n select the the position: ");
    scanf("%d",&val);
    if(val==1)
    {
        insert_beg();
        return;
    }
    temp=start;
    int i=1;
    while(temp!=NULL)
    {
        if(i==val)
        {
            t=1;
            create_node();
            printf("\n ENter the value: ");
            scanf("%d",&val);

            node->info=val;
            node->prev=prev;
            node->next=temp;
            prev->next=node;
            temp->prev=node;

            display();
            break;
        }
        i++;
        prev=temp;
        temp=temp->next;
    }
    if(t==0)
    {
        printf("\n wrong position inserted");
        display();
    }

}
void del_beg()
{
    if(start==NULL)
    {
        printf("\n Dll is EMpty for Delete");
        return;
    }
    printf("\n %d is deleted\n",start->info);
    node=start;
    start=start->next;
    free(node);
    display();
}
void del_end()
{
    if(start==NULL)
    {
        printf("\n Dll is empty for delete");
        return;
    }
    if(start->next==NULL)
    {
        del_beg();
        return;
    }
    temp=start;
    while(temp->next!=NULL)
    {
        prev=temp;
        temp=temp->next;
    }
    printf("\n %d is deleted\n",temp->info);
    prev->next=NULL;
    free(temp);
    display();
}
void del_the_value()
{
    int t=0;
    if(start==NULL)
    {
        printf("\n Dll is empty for delete");
        return;
    }
    printf("\n\n \t Choose the value you want to Delete");
    display();
    printf("\n \nENter the value: ");
    scanf("%d",&val);
    if(start->info==val)
    {
        del_beg();
        return;
    }
    temp=start;
    while(temp!=NULL)
    {
        if(temp->info==val)
        {
            t=1;
            prev->next=temp->next;
            printf("\n %d is deleted\n",temp->info);
            free(temp);
            display();
            break;
        }
        prev=temp;
        temp=temp->next;
    }
    if(t==0)
    {
        printf("\n Wrong value inserted");
        display();
    }

}
void del_the_posi()
{
    int t=0,l,i=16;
    if(start==NULL)
    {
        printf("\n the DLL is empty for delete");
        return;

    }
    printf("\n chose the position you want to delete:- ");
    display();
    printf("\n Enter the position: ");
    scanf("%d",&l);
    if(l==1)
    {
        del_beg();
        return;
    }
    temp=start;
    while(temp!=NULL)
    {
        if(i==l)
        {
            prev->next=temp->next;
            printf("\n %d is deleted\n",temp->info);
            free(temp);
            display();
            break;
        }
        i++;
        prev=temp;
        temp=temp->next;
    }
}
int main()
{
    int ch;
    do
    {
        printf("\n\t\t DLL menu");
        printf("\n 1.insert_beg");
        printf("\n 2.insert_end");
        printf("\n 3.insert_spc_value");
        printf("\n 4.insert_spc_position");
        printf("\n 5.delete_beg");
        printf("\n 6.delete_end");
        printf("\n 7.delete_spc_value");
        printf("\n 8.delete_spc_position");
        printf("\n 9.display");
        printf("\n Enter  your choice: ");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1:
                insert_beg();
                break;
            case 2:
                insert_end();
                break;
            case 3:
                insert_spc_val();
                break;
            case 4:
                insert_spc_posi();
                break;
            case 5:
                del_beg();
                break;
            case 6:
                del_end();
                break;
            case 7:
                del_the_value();
                break;
            case 8:
                del_the_posi();
                break;
            case 9:
                display();
        }

    }while(ch<=9 && ch>=1);

    return 0;
}