C++ Library - <set>-alljchome-开发者的教程家园

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C++ Library - <set>

Introduction

A set is an Associative container which contains a sorted set of unique objects of type Key. Each element may occur only once, so duppcates are not allowed.

There are four kind of Associative containers: set, multiset, map and multimap.

The value of the elements in a set cannot be modified once in the container, i.e., the elements are always const. But they can be inserted or removed from the container.

set containers are generally slower than unordered_set containers in accessing inspanidual elements by their key, but they allow the direct iteration on subsets based on their order.

Definition

Below is definition of std::set from <set> header file

template < 
    class Key,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<Key>
> class set;

Parameters

Key − Type of the element contained.

Key may be substituted by any other data type including user-defined type.

Member types

Following member types can be used as parameters or return type by member functions.

Sr.No.	Member types	Definition
1	key_type	Key
2	value_type	Key
3	reference	Allocator::reference value_type&
4	const_reference	Allocator::const_reference const value_type&
5	pointer	Allocator::pointer std::allocator_traits<Allocator>::pointer
6	const_pointer	Allocator::const_pointer std::allocator_traits<Allocator>::const_pointer
7	iterator	BidirectionalIterator
8	const_iterator	constant BidirectionalIterator
9	reverse_iterator	std::reverse_iterator <iterator>
10	const_reverse_iterator	std::reverse_iterator <const_iterator>
11	size_type	Unsigned Integer Type (std::size_t)
12	difference_type	Signed Integer Type (std::ptrdiff_t)
13	key_compare	Compare
14	value_compare	Compare
15	allocator_type	Allocator

Functions from <set>

Below is pst of all methods from <set> header.

MEMBER FUNCTIONS

DEFAULT MEMBER FUNCTIONS

Sr.No.	Method & Description
1	Default constructor Constructs the set container.
2	Range constructor Constructs the set container with contents of the range.
3	Copy constructor Constructs the set container with the copy of other set.
4	Move constructor Constructs the set container with the contents of other set using move semantics.
5	Initiapzer-pst constructor Constructs the set container with contents of the iniapzer pst.
6	(destructor) Destructs the set container.
7	operator= Assigns values to the set container.

ITERATORS

Sr.No.	Method & Description
1	set::begin Returns the iterator to beginning.
2	set::cbegin Returns the const iterator to beginning.
3	set::end Returns the iterator to end.
4	set::cend Returns the const iterator to end.
5	set::rbegin Returns the reverse iterator to reverse beginning.
6	set::crbegin Return const reverse iterator to reverse beginning.
7	set::rend Returns the reverse iterator to reverse end.
8	set::crend Returns the const reverse iterator to reverse end.

CAPACITY

Sr.No.	Method & Description
1	set::empty Returns wheteher the set container is empty.
2	set::size Returns the number of elements in the set container.
3	set::max_size Returns the maximum number of elements that the set container can hold.

MODIFIERS

Sr.No.	Method & Description
1	set::clear Removes all elements from the set container.
2	set::insert Inserts new element in the set container.
3	set::emplace Inserts new element in the set, if its unique.
4	set::emplace_hint Inserts new element in the set, if its unique, with a hint on the inserting position.
5	set::erase Removes either a single element or a range of elements from the set container.
6	set::swap Exchanges the content of the container by the content of another set container of the same type.

LOOKUP

Sr.No.	Method & Description
1	set::count Returns the number of elements with matching value in the set container.
2	set::find Searches the set container for value and returns an iterator to it if found, else returns an iterator to set::end.
3	set::lower_bound Returns an iterator pointing to the first element in the set container which is not considered to go before value.
4	set::upper_bound Returns an iterator pointing to the first element in the set container which is considered to go after value.
5	set::equal_range Returns the bounds of a range that includes all the elements in the set container that are equivalent to value.

OBSERVERS

Sr.No.	Method & Description
1	set::key_comp Returns a copy of the comparison object used by the set container.
2	set::value_comp Returns a copy of the comparison object used by the set container.

ALLOCATOR

Sr.No.	Method & Description
1	set::get_allocator Returns a copy of the allocator object associated with the set container.