Set (C++)

A set is an associative container data structure that is available as part of the C++ Standard Library (STL), and contains a sorted set of unique objects.

Although the abstract concept of a set does not necessarily imply an ordered collection, the standard library set data structure is always ordered. Its functionality in the STL is provided as a template class, such that any valid C++ object can be used with it. Sets are guaranteed to perform operations of insertion, deletion, and testing whether an element is in it, in logarithmic time - O(log n). As such, they are typically implemented using self-balancing binary search trees and support's bidirectional iterator

Types

There are 2 types of sets available in the C++ STL: Set and Multiset.

Set

In a set, every element is unique, and insertions of values that are already present in the container are ignored.

Multiset

In a multiset, multiple occurrences of the same value are allowed.

Characteristics

• Unique element value: In a set, no two values are same.
• Element value is itself a key.
• Elements follow strict weak ordering at all times.

Function's in Set

In a set container various functions are used. Some of them are as follows:

begin

Function begin() is used to return an iterator to the first element.It is constant time function.

• Syntax

#include<set>
iterator begin();
const_iterator begin const;

end

The function end() will return an iterator just before the end of the set. It is constant time function.

• Syntax

#include<set>
iterator end();
const_iterator end() const;

rbegin

function will return a reverse iterator to the end of current set. It is constant time function.

• syntax

#include<set>
reverse iterator rbegin();
const_reverse_iterator rbegin() const;

External links

• C++ reference for std::set