Flash cards
Review the key moves
What is the main idea behind C++ List?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
// ___ the list library #include <list>Put the learning moves in the order that makes the concept easiest to apply.
A list is similar to a vector in that it can store multiple elements of the same type and dynamically grow in size.
However, two major differences between lists and vectors are:
- You can add and remove elements from both the beginning and at the end of a list, while vectors are generally optimized for adding and removing at the end.
- Unlike vectors, a list does not support random access, meaning you cannot directly jump to a specific index, or access elements by index numbers.
// Include the list library #include <list>Create a List
To create a list, use the list keyword, and specify the type of values it should store within angle brackets <> and then the name of the list, like: list< type > listName .
Example
// Create a list called cars that will store strings list<string> cars;If you want to add elements at the time of declaration, place them in a comma-separated list, inside curly braces {} :
Example
// Create a list called cars that will store strings list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"}; // Print list elements
for (string car : cars) {
cout << car << "\n";
}Note
The type of the list ( string in our example) cannot be changed after its been declared.
Access a List
You cannot access list elements by referring to index numbers, like with arrays and vectors.
However, you can access the first or the last element with the .front() and .back() functions, respectively:
Example
// Create a list called cars that will store strings list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"}; // Get the first element cout << cars.front(); // Outputs Volvo // Get the last element cout << cars.back(); // Outputs MazdaChange a List Element
You can also change the value of the first or the last element with the .front() and .back() functions
Example
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
// Change the value of the first element cars.front() = "Opel"; // Change the value of the last element cars.back() = "Toyota"; cout << cars.front(); // Now outputs Opel instead of Volvo cout << cars.back(); // Now outputs Toyota instead of MazdaAdd List Elements
To add elements to a list, you can use .push_front() to insert an element at the beginning of the list and .push_back() to add an element at the end:
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
// Add an element at the beginning cars.push_front("Tesla"); // Add an element at the end cars.push_back("VW");Remove List Elements
To remove elements from a list, use .pop_front() to remove an element from the beginning of the list and .pop_back() to remove an element at the end:
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
// Remove the first element cars.pop_front(); // Remove the last element cars.pop_back();List Size
To find out how many elements a list has, use the .size() function:
Example
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
cout << cars.size();
// Outputs 4Check if a List is Empty
Use the .empty() function to find out if a list is empty or not.
The .empty() function returns 1 ( true ) if the list is empty and 0 ( false ) otherwise:
Example
list<string> cars;
cout << cars.empty();
// Outputs 1 (The list is empty)Example
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
cout << cars.empty();
// Outputs 0 (not empty)Loop Through a List
You cannot loop through the list elements with a traditional for loop combined with the .size() function, since it is not possible to access elements in a list by index:
Example
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
for (int i = 0; i < cars.size(); i++) {
cout << cars[i] << "\n";
}The simplest way to loop through a list is with the for-each loop:
Example
list<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};
for (string car : cars) {
cout << car << "\n";
}Tip
It is also possible to loop through lists with an iterator , which you will learn more about in a later chapter.