Cpp Standard Library 简明教程

C++ Library - <set>

Introduction

set 是一种关联容器，它包含了一个类型为 Key 的唯一对象的有序集合。每个元素只能出现一次，因此不允许重复元素。

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

关联容器有四种类型：集合、多重集合、映射和多重映射。

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

一旦添加到容器中，集合中元素的值就不能被修改，即，元素总是 const。但是，它们可以从容器中插入或删除。

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 容器通常较 unordered_set 容器访问单个元素慢，但允许直接根据元素顺序迭代子集。

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

Definition

以下是 <set> 标头文件中 std::set 的定义

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

  1. Key − Type of the element contained. Key may be substituted by any other data type including user-defined type.

Member types

以下成员类型可作为参数或返回类型，由成员函数使用。

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_pointerstd::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>

以下是 <set> 标头文件中所有方法的列表。

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

MEMBER FUNCTIONS

DEFAULT MEMBER FUNCTIONS

DEFAULT MEMBER FUNCTIONS

Sr.No.

Method & Description

1

Default constructorConstructs the set container.

2

Range constructorConstructs the set container with contents of the range.

3

Copy constructorConstructs the set container with the copy of other set.

4

Move constructorConstructs the set container with the contents of other set using move semantics.

5

Initializer-list constructorConstructs the set container with contents of the inializer list.

6

(destructor)Destructs the set container.

7

[role="bare"]../cpp_standard_library/cpp_set_operator=.htmlAssigns values to the set container.

ITERATORS

Sr.No.

Method & Description

1

set::beginReturns the iterator to beginning.

2

set::cbeginReturns the const iterator to beginning.

3

set::endReturns the iterator to end.

4

set::cendReturns the const iterator to end.

5

set::rbeginReturns the reverse iterator to reverse beginning.

6

set::crbeginReturn const reverse iterator to reverse beginning.

7

set::rendReturns the reverse iterator to reverse end.

8

set::crendReturns the const reverse iterator to reverse end.

CAPACITY

Sr.No.

Method & Description

1

set::emptyReturns wheteher the set container is empty.

2

set::sizeReturns the number of elements in the set container.

3

set::max_sizeReturns the maximum number of elements that the set container can hold.

MODIFIERS

Sr.No.

Method & Description

1

set::clearRemoves all elements from the set container.

2

set::insertInserts new element in the set container.

3

set::emplaceInserts new element in the set, if its unique.

4

set::emplace_hintInserts new element in the set, if its unique, with a hint on the inserting position.

5

set::eraseRemoves either a single element or a range of elements from the set container.

6

set::swapExchanges the content of the container by the content of another set container of the same type.

LOOKUP

Sr.No.

Method & Description

1

set::countReturns the number of elements with matching value in the set container.

2

set::findSearches the set container for value and returns an iterator to it if found, else returns an iterator to set::end.

3

set::lower_boundReturns an iterator pointing to the first element in the set container which is not considered to go before value.

4

set::upper_boundReturns an iterator pointing to the first element in the set container which is considered to go after value.

5

set::equal_rangeReturns 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_compReturns a copy of the comparison object used by the set container.

2

set::value_compReturns a copy of the comparison object used by the set container.

ALLOCATOR

Sr.No.

Method & Description

1

set::get_allocatorReturns a copy of the allocator object associated with the set container.