#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
struct node{
   int data;
   struct node *link;
}*head = NULL, *new_node, *ptr=NULL, *prev_ptr, *temp;

void insertBeg(){
        int info;
        new_node = (struct node*)malloc(sizeof(struct node));
        printf("nEnter data : ");
        scanf("%d",&info);
        new_node->data=info;
        new_node->link=NULL;
            if(head==NULL){
                head=new_node;
            }
            else{
                new_node->link=head;
                head=new_node;
            }
    }

    void insertEnd(){
        int info;
        new_node = (struct node*)malloc(sizeof(struct node));
        printf("nEnter data : ");
        scanf("%d",&info);
        new_node->data=info;
        if(head==NULL){
            head=new_node;
            new_node->link=NULL;
        }
        else{
            prev_ptr=head;
            ptr=head->link;
            while(ptr!=NULL){
                prev_ptr=ptr;
                ptr=ptr->link;
            }
            prev_ptr->link=new_node;
            new_node->link=NULL;
        }
    }

    void displayNode(){
        printf("nLinked List is : ");
        ptr=head;
        while(ptr!=NULL){
            printf("%d--->",ptr->data);
            ptr=ptr->link;
        }
    }

    void deleteBeg(){
        if(head==NULL){
            printf("nUnderflow");
        }
        else{
            temp=head;
            head=head->link;
            free(temp);
        }
    }

    void deleteEnd(){
        if(head==NULL){
            printf("nUnderflow");
        }
        else{
            prev_ptr=head;
            ptr=head->link;
            while(ptr!=NULL){
                prev_ptr=ptr;
                ptr=ptr->link;
            }
            prev_ptr->link=NULL;
            free(ptr);
        }
    }

    void traverse(){
        int count=0;
        ptr=head;
        while(ptr!=NULL){
            ptr=ptr->link;
            count++;
        }
        printf("nNumber of elements in the list are : %d",count);
    }

int main(){
        int choice,ch='y';
        label:
        printf("nPress 1 to insert at begn2 to insert at end");
        printf("n3 to delete from begn4 to delete from end");
        printf("n5 to display the listn6 to traverse the linked list : ");
        scanf("%d",&choice);
        switch(choice){
            case 1: insertBeg();
                break;
            case 2: insertEnd();
                break;
            case 3: deleteBeg();
                break;
            case 4: deleteEnd();
                break;
            case 5: displayNode();
                break;
            case 6: traverse();
                break;
            default: printf("nInvalid Option");
        }
        printf("nPress y to continue or any other key to exit : ");
        scanf("%s",&ch);
        if(ch=='y' || ch=='Y'){
            goto label;
        }
        getch();
        return 0;
    }