Question

Please answer in C

A doubly linked list is a list in which each entry contains a pointer to the preceding entry in the list as well as a pointer to the next entry in the list. Define the appropriate structure for the doubly linked list. Write a user space program that implements a doubly linked list and prints out the elements of the list. Develop insert_entry() and remove_entry() functions for this list. The link list should store information on runners at a track meet that are on lanes 1 through 8. Information such as bib number, name, school, qualifier time, etc. must be stored.

Answer 1

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

struct runner {
        int bib;
        char name[100];
};

struct node
{
        struct runner data;
        struct node *prev;
        struct node *next;
};
struct node *head;


void insert_entry(struct runner item) {
        struct node *ptr, *temp;
        ptr = (struct node *) malloc(sizeof(struct node));
        if (ptr == NULL)
                return;

        ptr->data = item;
        if (head == NULL)
        {
                ptr->next = NULL;
                ptr->prev = NULL;
                head = ptr;
        }
        else
        {
                temp = head;
                while (temp->next != NULL)
                {
                        temp = temp->next;
                }
                temp->next = ptr;
                ptr ->prev = temp;
                ptr->next = NULL;
        }


}


void remove_entry() {
        struct node *ptr;
        if (head == NULL)
                return;

        if (head->next == NULL)
        {
                head = NULL;
                free(head);
        }
        else
        {
                ptr = head;
                if (ptr->next != NULL)
                {
                        ptr = ptr -> next;
                }
                ptr -> prev -> next = NULL;
                free(ptr);
        }
}

void display() {
        struct node *ptr;
        printf("...Runners...\n\n");
        ptr = head;
        while (ptr != NULL)
        {
                printf("BIB Number: %d\t Name: %s\n", ptr->data.bib,ptr->data.name);
                ptr = ptr->next;
        }
}

int main ()  {

        struct runner a;
        a.bib = 1;
        strcpy(a.name,"Michael");
        insert_entry(a);

        a.bib = 2;
        strcpy(a.name,"Ramos");
        insert_entry(a);
        a.bib = 3;
        strcpy(a.name,"Messi");
        insert_entry(a);
        a.bib = 4;
        strcpy(a.name,"Benzema");
        insert_entry(a);
        a.bib = 5;
        strcpy(a.name,"Cristiano");
        insert_entry(a);
        a.bib = 6;
        strcpy(a.name,"Ronaldhino");
        insert_entry(a);
        a.bib = 7;
        strcpy(a.name,"Ambape");
        insert_entry(a);
        a.bib = 8;
        strcpy(a.name,"Neymar");
        insert_entry(a);

        display();
        return 0;
}

OUTPUT: