C++ List

C++ List is a STL container that stores elements randomly in unrelated locations. To maintain sequential ordering, every list element includes two links:

• one that points to the previous element
• another that points to the next element

In C++, the STL list implements the doubly-linked list data structure. As a result, we can iterate both forward and backward.

Create C++ STL List

To create a list, we need to include the list header file in our program.

#include<list>

Once we import the header file, we can now declare a list using the following syntax:

std::list<Type> list_name = {value1, value2, ...};

Here,

• std::list - declares a STL container of type list
• <Type> - the data type of the values to be stored in the list
• list_name - a unique name given to the list
• value1, value2, ... - values to be stored in the list

Let's see an example,

// create a list of integer type
std::list<int> numbers = {1, 2, 3, 4, 5};

// create a list of character type
std::list<char> vowels = {'a', 'e', 'i', 'o', 'u'};

std::list<int> {1, 2, 3, 4, 5};

Example: C++ STL List

Output

List Elements: 1, 2, 3, 4,

In the above example, we have created a list named numbers with elements: 1, 2, 3, 4. We then used a ranged for loop to print the list elements.

Note: We have used list instead of std::list because we have already defined std namespace using using namespace std;.

Basic operations on List

C++ STL provides various functions that we can use to perform different operations on lists. Let's look at some commonly used list functions to perform the following operations:

1. Add elements
2. Access elements
3. Remove elements

1. Add Elements to a List in C++

We can add values in a list using the following functions:

• push_front() - inserts an element to the beginning of the list
• push_back() - adds an element to the end of the list

Let's see an example,

Output

Initial List: 1, 2, 3, 
Final List: 0, 1, 2, 3, 4,

2. Access List Elements

We can access list elements using the following functions:

• front() - returns the first element of the list
• back() - returns the last element of the list

Let's see an example,

Output

First Element: 1
Last Element: 5

3. Delete List Elements

We can delete list elements using the following functions:

• pop_front() - removes the element at the beginning of the list
• pop_back() - removes the element at the end of the list

Here's an example,

Output

Inital List: 1,  2,  3,  4,  5,  
Final List: 2, 3, 4, 

Other List Functions in C++

While there are many functions that can be used with lists, we will only look at some of the functions in the table below:

Access elements using an iterator

We can use iterators to access a list element at a specified position. For example,

Output

Second Element: 2
Fourth Element: 4

In the above example,

• list<int>::iterator - defines an iterator for a list of int type
• numbers.begin() - sets the iterator to point to the beginning of the list

Notice that we have used ++itr; repeatedly instead of adding an integer to itr like itr+3;.

This is because iterators are not simple numeric values like regular integers. They point to specific memory locations in the container.

Incrementing an iterator with the ++ operator makes it point to the next element in the container.

To learn more about iterators, visit C++ STL Iterators.

list_name.insert(iterator, value);

Initial List: 1, 2, 3, 
Final List: 1, 2, 0, 3,

list_name.remove(element);

Initial List: 1, 2, 1, 3, 4, 1, 
Final List: 2, 3, 4, 

Initial List: 0, 1, 2, 3, 4, 5, 3, 
Final List: 0, 1, 2, 4, 5,