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Efficient Lookups: Unordered maps provide average O ( 1 ) O(1) O ( 1 ) time complexity for lookups. This means retrieving a contact&#x27;s phone number by name is very fast, even with a large number of contacts.
Uniqueness: Unordered maps inherently ensure that keys (in this case, contact names) are unique. This prevents duplicate entries and simplifies data integrity management.
Readability: The syntax for accessing unordered map entries is straightforward and highly readable. This makes the code easier to understand and maintain.
Flexibility: Unordered maps in C++ are versatile and can hold a variety of data types as values. This flexibility allows for easily extending the address book to store additional information, such as email addresses or physical addresses, if needed in the future.

Introduction

Welcome! Today, we will explore creating a simple address book application using C++ and its std::unordered_map class. This task will help you understand how to manipulate unordered maps in C++, focusing on adding, retrieving, and deleting entries. By the end of this lesson, you'll have a solid grasp of these fundamental operations.

Introducing Methods to Implement

In this task, we will implement three methods to manage our address book:

bool add_contact(const std::string& name, const std::string& phone_number): Adds a new contact. Returns false if the contact already exists; otherwise, adds the contact and returns true. In this task, let's assume phone numbers do not change, so it's not allowed to overwrite the existing contact's number.
std::string get_contact(const std::string& name): Retrieves the phone number for a given name. Returns an empty string if the contact does not exist.
bool delete_contact(const std::string& name): Deletes a contact with the given name. Returns true if the contact exists and is deleted, false otherwise.

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