LinkedList Header Definition

The underlying data structure is a singly linked list. We define the node structure to hold generic data, which will be specialized for the contact information later.

#ifndef LINKED_LIST_H
#define LINKED_LIST_H

#include <stdlib.h>
#include <assert.h>
#include "AddressBook.h"

typedef ContactData Item;

typedef struct Node {
    Item data;
    struct Node* next;
} Node;

// Fundamental list operations
void list_push_back(Node** head_ref, Item value);
void list_push_front(Node** head_ref, Item value);
void list_pop_back(Node** head_ref);
void list_pop_front(Node** head_ref);
void list_insert_after(Node* pos, Item value);
void list_erase(Node** head_ref, Node* pos);
void list_destroy(Node** head_ref);

#endif

Address Book Interface

This header defines the specific data structure for a contact and exposes the high-level API for managing the address book.

#ifndef ADDRESS_BOOK_H
#define ADDRESS_BOOK_H

#define MAX_NAME_LEN 32
#define MAX_PHONE_LEN 16

typedef struct ContactData {
    char name[MAX_NAME_LEN];
    char phone[MAX_PHONE_LEN];
} ContactData;

// The list itself is represented by a pointer to the head node
typedef Node* AddressBook;

void create_book(AddressBook* book);
void add_entry(AddressBook* book);
void remove_entry(AddressBook* book);
void display_book(AddressBook book);
void update_entry(AddressBook* book);
void delete_book(AddressBook* book);

#endif

Implementation Logic

The following source file implements the logic required to manipulate the linked list as an address book. It handles user input, memory management, and traversal logic.

#include "AddressBook.h"
#include "LinkedList.h"
#include <stdio.h>
#include <string.h>

void create_book(AddressBook* book) {
    *book = NULL;
}

void add_entry(AddressBook* book) {
    ContactData new_entry;
    printf("Input Name: ");
    scanf("%31s", new_entry.name);
    printf("Input Phone Number: ");
    scanf("%15s", new_entry.phone);
    
    list_push_back(book, new_entry);
}

void remove_entry(AddressBook* book) {
    char target[MAX_NAME_LEN];
    printf("Enter name of contact to delete: ");
    scanf("%31s", target);

    Node* current = *book;
    Node* previous = NULL;

    // Traverse the list to find the node
    while (current != NULL) {
        if (strcmp(current->data.name, target) == 0) {
            if (previous == NULL) {
                // Removing the head node
                *book = current->next;
            } else {
                previous->next = current->next;
            }
            free(current);
            printf("Contact removed successfully.\n");
            return;
        }
        previous = current;
        current = current->next;
    }
    printf("Error: Contact not found.\n");
}

void display_book(AddressBook book) {
    Node* iterator = book;
    if (!iterator) {
        printf("The address book is empty.\n");
        return;
    }

    printf("%-20s %-15s\n", "Name", "Phone");
    printf("-------------------------------\n");
    while (iterator != NULL) {
        printf("%-20s %-15s\n", iterator->data.name, iterator->data.phone);
        iterator = iterator->next;
    }
}

void update_entry(AddressBook* book) {
    char target[MAX_NAME_LEN];
    printf("Enter name of contact to modify: ");
    scanf("%31s", target);

    Node* iterator = *book;
    while (iterator != NULL) {
        if (strcmp(iterator->data.name, target) == 0) {
            printf("Enter new Name: ");
            scanf("%31s", iterator->data.name);
            printf("Enter new Phone: ");
            scanf("%15s", iterator->data.phone);
            printf("Contact updated.\n");
            return;
        }
        iterator = iterator->next;
    }
    printf("Error: Contact not found.\n");
}

void delete_book(AddressBook* book) {
    list_destroy(book);
}