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📅 最后修改于: 2020-12-15 04:33:59 🧑 作者: Mango

地图介绍

地图就像数据结构的字典。它是(键，值)对的序列，其中每个唯一键仅与单个值相关联。它通常被称为关联数组。

在地图中，键值通常用于对元素进行排序。对于地图数据，键和值的类型可以不同，它表示为

typedef pair value_type;

映射通常实现为二进制搜索树。

零尺寸的地图也是有效的。在这种情况下，map.begin()和map.end()指向同一位置。

定义

下面是头文件中std :: map的定义

template < class Key,
           class T,
           class Compare = less,
           class Alloc = allocator >
           > class map;

参量

密钥–密钥的类型。
T-映射值的类型。
比较-一个二进制谓词，它使用两个元素键作为参数并返回布尔值。
Alloc-分配器对象的类型。

T可以用任何其他数据类型(包括用户定义的类型)代替。

会员类型

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 (First parameter of the template)
2	mapped_type	T (Second parameter of the template)
3	key_compare	Compare (Third parameter of the template)
4	allocator_type	Alloc (Fourth parameter of the template)
5	value_type	pair
6	value_compare	Nested function class to compare elements
7	reference	allocator_type::reference
8	const_reference	allocator_type::const_reference
9	pointer	allocator_type::pointer
10	const_pointer	allocator_type::const_pointer
11	iterator	bi-directional iterator to `value_type`
12	const_iterator	bi-directional iterator to const `value_type`
13	reverse_iterator	reverse iterator
14	const_reverse_iterator	constant reverse iterator
15	difference_type	ptrdiff_t
16	size_type	size_t

中的功能

以下是标头中的所有方法的列表。

建设者

Sr.No.	Method & Description
1	map::map `default constructor` Constructs an empty map with zero elements.
2	map::map `range constructor` Constructs a map with as many elements as in range of `first` to `last`.
3	map::map `copy constructor` Constructs a map with copy of each elements present in existing map.
4	map::map `move constructor` Constructs a map with the contents of other using move semantics.
5	map::map `initializer list constructor` Constructs a map from initialize list.

析构函数

Sr.No.	Method & Description
1	map::~map Destroys map object by deallocating it’s memory.

会员职能

Sr.No.	Method & Description
1	map::at Returns a reference to the mapped value associated with key `k`.
2	map::begin Returns a iterator which refers to the first element of the map.
3	map::cbegin Returns a constant iterator which refers to the first element of the map.
4	map::cend Returns a constant iterator which points to `past-the-end` element of the map.
5	map::clear Destroys the map by removing all elements and sets size of map to zero.
6	map::count Returns number of mapped values associated with key `k`.
7	map::crbegin Returns a constant reverse iterator which points to the last element of the container i.
8	map::crend Returns a constant reverse iterator which points to the theoretical element preceding the first element in the container i.
9	map::emplace Extends container by inserting new element.
10	map::emplace_hint `hint version` Inserts a new element in a map using hint as a position for element.
11	map::empty Tests whether map is empty or not.
12	map::end Returns an iterator which points to `past-the-end` element in the map.
13	map::equal_range Returns range of elements that matches specific key.
14	map::erase `position version` Removes single element of the map from `position`.
15	map::erase `position version` Removes single element of the map from `position`.
16	map::erase `key` Removes mapped value associated with key `k`.
17	map::erase `range version` Removes range of element from the the map.
18	map::erase `range version` Removes range of element from the the map.
19	map::find Finds an element associated with key `k`.
20	map::get_allocator Returns an allocator associated with map.
21	map::insert `single element` Extends container by inserting new element in map.
22	map::insert `hint version` Extends container by inserting new element in map.
23	map::insert `range version` Extends container by inserting new elements in the map.
24	map::insert `move hint verstion` Extends map by inserting new element.
25	map::insert `initializer list version` Extends map by inserting new element from initializer list.
26	map::key_comp Returns a function object that compares the keys, which is a copy of this container’s constructor argument `comp`.
27	map::lower_bound Returns an iterator pointing to the first element which is not less than key `k`.
28	map::max_size Returns the maximum number of elements can be held by map.
29	map::operator= `copy version` Assign new contents to the map by replacing old ones and modifies size if necessary.
30	map::operator= `move version` Move the contents of one map into another and modifies size if necessary.
31	map::operator= `initializer list version` Copy elements from initializer list to map.
32	map::operator[] `copy version` If key `k` matches an element in the container, then method returns a reference to the element.
33	map::operator[] `move version` If key `k` matches an element in the container, then method returns a reference to the element.
34	map::rbegin Returns a reverse iterator which points to the last element of the map.
35	map::rend Returns a reverse iterator which points to the reverse end of the map i.
36	map::size Returns the number of elements present in the map.
37	map::swap Exchanges the content of map with contents of map x.
38	map::upper_bound Returns an iterator pointing to the first element which is greater than key `k`.
39	map::value_comp Returns a function object that compares objects of type `std::map::value_type`.

非成员重载函数

Sr.No.	Method & Description
1	operator== Tests whether two maps are equal or not.
2	operator!= Tests whether two maps are equal or not.
3	operator< Tests whether first map is less than other or not.
4	map::operator<= Tests whether first map is less than or equal to other or not.
5	operator> Tests whether first map is greater than other or not.
6	operator>= Tests whether first map is greater than or equal to other or not.
7	swap() Exchanges the content of map with contents of map x.

多图简介

Multimap是类似于数据结构的字典。它是(键，值)对的序列，其中多个值可以与等效键关联。它通常被称为关联数组。

在多地图中，键值通常用于对元素进行排序。对于多图数据，键和值的类型可以不同，并表示为

typedef pair value_type;

多图通常实现为二进制搜索树。

零尺寸的多图也有效。在这种情况下，multimap.begin()和multimap.end()指向同一位置。

定义

下面是头文件中std :: multimap的定义

template < class Key,
           class T,
           class Compare = less,
           class Alloc = allocator >
           > class multimap;

参量

密钥–密钥的类型。
T-映射值的类型。
比较-一个二进制谓词，它使用两个元素键作为参数并返回布尔值。
Alloc-分配器对象的类型。