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📅 最后修改于: 2020-12-15 04:35:23 🧑 作者: Mango

介绍

集合是一个关联容器，其中包含一组排序的键类型的唯一对象。每个元素只能出现一次，因此不允许重复。

关联容器有四种：set，multiset，map和multimap。

集合中元素的值不能在容器中一次修改，即，元素始终为const。但是可以将它们插入容器或从容器中取出。

集合容器在通过键访问单个元素方面通常比unordered_set容器慢，但是它们允许基于子集的顺序直接迭代子集。

下面是头文件中std :: set的定义

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

成员函数可以将以下成员类型用作参数或返回类型。

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::pointer
6	const_pointer	Allocator::const_pointer std::allocator_traits::const_pointer
7	iterator	BidirectionalIterator
8	const_iterator	constant BidirectionalIterator
9	reverse_iterator	std::reverse_iterator
10	const_reverse_iterator	std::reverse_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

以下是标头中所有方法的列表。

默认会员功能

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	Initializer-list constructor Constructs the set container with contents of the inializer list.
6	(destructor) Destructs the set container.
7	operator= Assigns values to the set container.

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.

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.

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.

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.

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.

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