# Lecture 3 --- Classes

- Classes in C++; Types and defining new types; Example: A Date class;
- Class declaration: member variables and member functions; Using the class member functions;
- Member function implementation; Class scope; Classes vs. structs; Designing classes;
- Defining a custom sort of class instances.

## 3.1 Types and Defining New Types	

- Every C++ object has a type (e.g., integers, doubles, strings, and vectors, etc., including custom types); and a class is a custom data type, also known as a user-defined data type.
– The type tells us what the data means and what operations can be performed on the data.

## 3.2 C++ Classes

- A C++ class group together variables and functions that operate on those variables. We call these variables *member variables*, and we call these functions *member functions*.

- A C++ class consists of

  – a collection of member variables, usually private, and
  – a collection of member functions, usually public, which operate on these variables.

- public member functions can be accessed directly from outside the class,
- private member functions and member variables can only be accessed indirectly from outside the class, through public member functions.

## 3.3 Class scope notation

## 3.4 Constructors

## 3.5 Member Functions

## 3.6 Constant member functions	

## 3.7 Classes vs. structs

## 3.8 Designing and implementing classes

## 3.9 Providing Comparison Functions to Sort

## 3.10 Operator Overloading

## 3.11 Exercises

- [Leetcode problem 8: String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)
- [Leetcode problem 211: Design Add and Search Words Data Structure](https://leetcode.com/problems/design-add-and-search-words-data-structure/)
- [Leetcode problem 1662: Check If Two String Arrays are Equivalent](https://leetcode.com/problems/check-if-two-string-arrays-are-equivalent/)