#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>

struct Node{
    int info;
    struct Node *next;
};

typedef struct Node NodeType;

// Two glboal variables to store address of first and last nodes.
NodeType *first =NULL , *last = NULL;


NodeType* getNode(){
    NodeType *ptr;
    ptr = (NodeType *) malloc(sizeof(NodeType));
    return ptr;
}

void createEmptyList(NodeType *first){
    first =NULL;
    printf("\nList is emptied.\n");
}

void insertatBegin(int item){
    NodeType *newnode;
    NodeType *temp;

    temp = first; //hold the address of the first node of list(which is already present)

    newnode = getNode(); //creates the new node

    newnode ->info = item; //info section of new node

    //filling next(address) section of new node
    if(first ==NULL){ //if the linked list is empty i.e. first address is null
        newnode ->next =NULL;
        first = last = newnode; //there is only one node so first and last is same node
    }

    else{ //if not empty
        newnode ->next = temp;
        first = newnode;
    }

}


void insertatEnd(int item){
    NodeType *newnode;
    newnode =getNode();

    newnode -> info =item;
    newnode -> next =NULL;

    if (first == NULL) {
        first = newnode;
        last = newnode;
    }

    else
    {
        last -> next = newnode;
        last = newnode;
    }

}


void displayElements(){
    NodeType *temp;


    if (first == NULL) {
        printf("\n Linked list is empty.\n");
        exit(1);
    }

    else
    {
        while(temp != NULL){
            printf("%d\t",temp->info);
            temp = temp ->next;
        }

    }


}


int main(int argc, char const *argv[])
{
    int  item,ch;



    while(1){
        printf("\n---------------------------------\n");
        printf("\nOperations on singly linked list\n");
        printf("\n---------------------------------\n");
        printf("\n0.Make List Empty");
        printf("\n1.Insert node at first");
        printf("\n2.Insert node at last");
        printf("\n3.Insert node at position");
        printf("\n4.Delete first Node");
         printf("\n5.Delete last node");
        printf("\n6.Delete Node from any Position");
        printf("\n7.Sum of all data(info) of nodes");
        printf("\n8.Count no. of nodes");
        printf("\n9.Search Element in the linked list");
        printf("\n10.Display List from Beginning to end");
        printf("\n11.Exit\n");
        printf("\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");

        printf("Enter your choice : ");
        scanf("%d",&ch);


        switch (ch)
        {
            case 0:
                createEmptyList(first);
                break;


            case 1:
              printf("Enter the item to be inserted : ");
              scanf("%d",&item);
              insertatBegin(item);
                break;


            case 2:
             printf("Enter the item to be inserted : ");
              scanf("%d",&item);
              insertatEnd(item);
                break;



            case 3:

                break;


            case 4:

                break;


            case 5:

                break;


            case 6:

                break;


            case 7:

                break;


            case 8:

                break;


            case 9:

                break;


            case 10:
                displayElements();


                break;

            case 11:
              exit(1);


            default:
                break;
        }
    }





    return 0;
}