Question

The STL stack is considered a container adapter. What does that mean?

Short answer

Short Answer: A container adapter in the context of the STL stack is a class that modifies the behavior of an underlying STL container to implement a specific access pattern, in this case, the LIFO (Last In, First Out) access pattern. The STL stack provides a limited interface exposing only stack-related methods like push, pop, top, and size, restricting access to the underlying container's methods. Essentially, it modifies or adds specific behavior to an existing STL container without altering the container class itself.

Step-by-step solution

Understanding STL Containers

STL containers are a set of C++ template classes that provide common data structures like vectors, lists, and queues. These containers are used to store data during the program execution. In general, STL containers can be divided into Sequence Containers (e.g. Vector, List, Deque) and Associative Containers (e.g. Set, Map, Multiset), each type having different properties and being suitable for different tasks in programming.

Explaining Container Adapters

Container adapters are classes that implement a specific interface or behavior using an underlying container, modifying how the basic container methods are accessed. They have a restricted interface in comparison to the underlying container. Basically, container adapters are used to alter or add a specific behavior to an existing STL container, without modifying the original container class.

STL Stack as a Container Adapter

The STL stack is a container adapter, meaning it provides a modified behavior of an underlying STL container to implement the LIFO (Last In, First Out) access pattern. A stack is a data structure in which elements are added (pushed) or removed (popped) only from one end, called the top of the stack. Any underlying container (e.g. deque or vector) can be used by the stack, but in practice, the default container used is deque. The STL stack restricts the interface of the underlying container to only expose the stack-related methods such as push, pop, top, and size. In summary, stacks use another STL container to store their elements and provide a limited interface to exhibit LIFO behavior.