Containers in C++ STL

Last Updated : 03 Mar, 2025

Standard Template Library (STL) provides the built-in implementation of commonly used data structures known as containers. A container is a holder object that stores a collection of other objects (its elements). They are implemented as class templates, which allows great flexibility in the data types supported.

A container manages the storage space for its elements and provides member functions for easy access to useful operations.

Types of STL Containers

STL containers are divided into the following categories:

Sequence Containers
Associative Containers
Unordered Containers
Container Adapters

1. Sequence Containers

Sequence containers implement linear data structures in which the elements can be accessed sequentially. Following are the sequence containers in C++ STL:

Container Name	Description
Array	Container that wraps over fixed size static array.
Vector	Automatically resizable dynamic array.
Deque	Dynamic array of fixed-size arrays that allows fast insertions and deletions at both ends.
List	Implementation of Doubly Linked List data structure.
Forward List	Implementation of Singly Linked List data structure.

2. Associative Containers

Associative containers store data in some sorted order. It provides fast search, insert and delete in O(log n) time by using balanced trees like Red Black Trees.

Container Name	Description
Set	Collection of unique elements sorted on the basis of their values.
Map	Collection of key-value pairs sorted on the basis of the keys where no two pairs have same keys.
Multiset	Collection of elements sorted on the basis of their values but allows multiple copies of values.
Multimap	Collection of key-value pairs sorted on the basis of the keys where multiple pairs can have same keys.

3. Unordered Associative Containers

Unordered associative containers implement unsorted hashed data structures that can be quickly searched (O(1) amortized, O(n) worst-case complexity).

Container Name	Description
Unordered Set	Collection of unique elements hashed by their values.
Unordered Map	Collection of key-value pairs that are hashed by their keys where no two pairs have same keys.
Unordered Multiset	Collection of elements hashed by their values and allows multiple copies of values.
Unordered Multimap	Collection of key-value pairs that are hashed by their keys where multiple pairs can have same keys.

4. Container Adapters

Container adapters provide a different interface for other containers. They adapt the behavior of underlying containers to fit specific use cases.

Container Name	Description
Stack	Adapts a container to provide stack (LIFO) data structure.
Queue	Adapts a container to provide queue (FIFO) data structure.
Priority Queue	Adapts a container to provide heap data structure.

To master C++ Standard Template Library (STL) in the most efficient and effective way, do check out this C++ STL Online Course by GeeksforGeeks. The course covers the basics of C++ and in-depth explanations to all C++ STL containers, iterators, etc along with video explanations of a few problems. Also, you’ll learn to use STL inbuilt classes and functions in order to implement some of the complex data structures and perform operations on them conveniently.

Introduction to Iterators in C++

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Containers in C++ STL

Types of STL Containers

1. Sequence Containers

2. Associative Containers

3. Unordered Associative Containers

4. Container Adapters

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