CSCI 383 Object-Oriented Programming & Design Lecture 25 Martin van Bommel

Associative Containers Provide direct access to store and retrieve elements via keys (often called search keys) Each associate container maintains its keys in sorted order Implemented as a (self-balancing) Binary Search Tree (BST) Time complexity of Find, Insert, Delete ? The ordering of the elements is determined by a comparator function object Default is less If f is an object of class less and x and y are objects of class T, then f(x,y) returns true if x < y and false otherwise If T is a user-defined type (e.g., Student ), must provide overloading of operator<

Associative Containers The four associative containers are set, multiset map, multimap Iterating through an associative container traverses it in the sort order for that container

Set & Multiset Simple associative containers, meaning that elements are their own keys (i.e., a key is not associated with any additional value) Maintain keys in sorted order Provide set operations Union Intersection Difference Symmetric difference Handout #15

Map & Multimap Pair associate containers, meaning that its value type is a pair (often called key/value pair) Duplicate keys are allowed in a multimap, so multiple values can be associated with a single key (i.e., a one-to-many relationship) Duplicate keys are not allowed in a map, a single value can be associated with each key (i.e., a one-to-one mapping) Also known as an associative array, providing key in map ’s subscript operator[] locates value associated with key Handout #15

Container Adaptors They are not containers, but adapt other containers Do not provide the actual data structure implementation in which elements can be stored Provide restricted subset of container functionality Do not support iterators A benefit of an adaptor class is that you can choose an appropriate underlying data structure A stack is implemented with a deque by default but this can be changed with a second argument in constructor, e.g., vector instead of deque

Adaptor Containers The STL provides three adaptor containers stack queue priority_queue All three adaptor classes provide member functions push, pop and top that properly insert an element, remove an element, and check the “top” element (some implementations of queue use front to get a reference to the “first” element) Handout #16

bitset A special container designed to store bits (i.e., elements with only two possible values: 0 or 1, true or false,...) Very useful for representing a set of bit flags Very similar to a regular array, but optimizing for space allocation Each element occupies only one bit, which is eight times less than the smallest elemental type in C++ (i.e., char ) bitset s are fixed in size at compile time (i.e., unlike vector which allows for dynamic resizing)

Sieve of Eratosthenes A simple and ancient algorithm for finding all prime numbers up to a specified integer Created by Eratosthenes, an ancient Greek mathematician ALGORITHM (Done in class)