task3.cpp

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <limits>

using namespace std;

struct Contact {
    int id;
    string name;
    string phone;
    string email;
    string address;
};

vector<Contact> contacts;

// Save contacts to file
void saveContacts() {
    ofstream file("contacts.dat");

    for (const Contact &contact : contacts) {
        file << contact.id << '\n';
        file << contact.name << '\n';
        file << contact.phone << '\n';
        file << contact.email << '\n';
        file << contact.address << '\n';
    }

    file.close();
}

// Load contacts from file
void loadContacts() {
    ifstream file("contacts.dat");

    if (!file) {
        return;
    }

    Contact contact;

    while (file >> contact.id) {
        file.ignore(numeric_limits<streamsize>::max(), '\n');

        getline(file, contact.name);
        getline(file, contact.phone);
        getline(file, contact.email);
        getline(file, contact.address);

        contacts.push_back(contact);
    }

    file.close();
}

// Add new contact
void addContact() {
    Contact contact;

    cout << "\nEnter Contact ID: ";
    cin >> contact.id;

    // Check duplicate ID
    for (const Contact &c : contacts) {
        if (c.id == contact.id) {
            cout << "Contact ID already exists!\n";
            return;
        }
    }

    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    cout << "Enter Name: ";
    getline(cin, contact.name);

    cout << "Enter Phone Number: ";
    getline(cin, contact.phone);

    cout << "Enter Email: ";
    getline(cin, contact.email);

    cout << "Enter Address: ";
    getline(cin, contact.address);

    contacts.push_back(contact);

    saveContacts();

    cout << "\nContact added successfully!\n";
}

// Display all contacts
void displayContacts() {
    if (contacts.empty()) {
        cout << "\nNo contacts found.\n";
        return;
    }

    cout << "\n========== ALL CONTACTS ==========\n";

    for (const Contact &contact : contacts) {

        cout << "\nContact ID : " << contact.id;
        cout << "\nName       : " << contact.name;
        cout << "\nPhone      : " << contact.phone;
        cout << "\nEmail      : " << contact.email;
        cout << "\nAddress    : " << contact.address;

        cout << "\n----------------------------------\n";
    }
}

// Search contact by ID
void searchContact() {
    int id;

    cout << "\nEnter Contact ID to search: ";
    cin >> id;

    for (const Contact &contact : contacts) {

        if (contact.id == id) {

            cout << "\nContact Found!\n";

            cout << "Contact ID : " << contact.id << '\n';
            cout << "Name       : " << contact.name << '\n';
            cout << "Phone      : " << contact.phone << '\n';
            cout << "Email      : " << contact.email << '\n';
            cout << "Address    : " << contact.address << '\n';

            return;
        }
    }

    cout << "\nContact not found!\n";
}

// Update contact
void updateContact() {
    int id;

    cout << "\nEnter Contact ID to update: ";
    cin >> id;

    for (Contact &contact : contacts) {

        if (contact.id == id) {

            cin.ignore(numeric_limits<streamsize>::max(), '\n');

            cout << "Enter New Name: ";
            getline(cin, contact.name);

            cout << "Enter New Phone Number: ";
            getline(cin, contact.phone);

            cout << "Enter New Email: ";
            getline(cin, contact.email);

            cout << "Enter New Address: ";
            getline(cin, contact.address);

            saveContacts();

            cout << "\nContact updated successfully!\n";

            return;
        }
    }

    cout << "\nContact not found!\n";
}

// Delete contact
void deleteContact() {
    int id;

    cout << "\nEnter Contact ID to delete: ";
    cin >> id;

    for (auto it = contacts.begin(); it != contacts.end(); ++it) {

        if (it->id == id) {

            contacts.erase(it);

            saveContacts();

            cout << "\nContact deleted successfully!\n";

            return;
        }
    }

    cout << "\nContact not found!\n";
}

// Main function
int main() {

    loadContacts();

    int choice;

    do {

        cout << "\n\n====================================\n";
        cout << "       CONTACT MANAGEMENT SYSTEM\n";
        cout << "====================================\n";
        cout << "1. Add Contact\n";
        cout << "2. Display All Contacts\n";
        cout << "3. Search Contact\n";
        cout << "4. Update Contact\n";
        cout << "5. Delete Contact\n";
        cout << "6. Exit\n";
        cout << "====================================\n";

        cout << "Enter your choice: ";
        cin >> choice;

        switch (choice) {

            case 1:
                addContact();
                break;

            case 2:
                displayContacts();
                break;

            case 3:
                searchContact();
                break;

            case 4:
                updateContact();
                break;

            case 5:
                 deleteContact();
                 break;

            case 6:
                cout<<"\nThank you for using Contact Management System !\n";
                break;
                default:
                cout<<"\nInvalid choice Please try again.\n";
        }
    } while(choice!=6);
    return 0;
}