Containers

In C++, the Standard Template Library (STL) provides a collection of containers that are data structures used to store and organize data efficiently.

STL containers are part of the C++ Standard Library and offer various data structures with different capabilities to suit specific needs.

They are implemented using templates, which allows them to work with different types of data.

STL containers can be broadly categorized into three main types based on their properties and usage:

Sequence Containers:

• Sequence containers maintain the order of elements as they are inserted.
• The elements can be accessed using an index or iterator.
• Some commonly used sequence containers are:
  • std::vector: A dynamic array that can resize automatically.
  • std::deque: Double-ended queue, similar to a vector but allows efficient insertion and deletion at both ends.
  • std::list: Doubly linked list, optimized for insertion and deletion in the middle.
  • std::forward_list: Singly linked list, optimized for insertion and deletion at the front.

Associative Containers:

• Associative containers store elements in a sorted order based on certain criteria defined by a comparison function.
• They allow fast retrieval of elements using keys.
• Some commonly used associative containers are:
  • std::set: A set of unique elements sorted in ascending order.
  • std::map: A collection of key-value pairs sorted by the keys.
  • std::multiset: A set of elements that allows duplicates and is sorted.
  • std::multimap: A map that allows duplicate keys.

Unordered Containers:

• Unordered containers store elements in an unordered manner, providing fast retrieval based on the hash value of keys.
• They are typically implemented as hash tables.
• Some commonly used unordered containers are:
  • std::unordered_set: An unordered set of unique elements.
  • std::unordered_map: An unordered collection of key-value pairs.
  • std::unordered_multiset: An unordered set that allows duplicates.
  • std::unordered_multimap: An unordered map that allows duplicate keys.

Each type of container offers different characteristics and trade-offs in terms of memory usage, retrieval speed, insertion and deletion efficiency, and iterator stability. Choosing the right container depends on the specific requirements and performance needs of the application.

It is essential to be familiar with the properties and operations of different containers to effectively use the STL and write efficient and maintainable code. STL containers provide a consistent and convenient interface, making them powerful tools for managing data in C++ applications.