📅 最后修改于: 2020-12-15 04:36:27 🧑 作者: Mango
它是一个关联容器，不按特定顺序存储唯一元素，并且允许根据其值快速检索单个元素。
以下是std :: unordered_set的定义
template < class Key,
class Hash = hash,
class Pred = equal_to,
class Alloc = allocator
> class unordered_set;
键-它定义元素的类型。
哈希-它是一元函数对象。
Pred-这是一个二进制谓词，它接受与元素相同类型的两个参数，并返回布尔值。
的Alloc -它定义allowcater的类型。
成员函数可以将以下成员类型用作参数或返回类型。
| member type | definition | notes |
|---|---|---|
| key_type | It is the first template parameter (Key) | |
| value_type | It is the first template parameter (Key) | The same as key_type |
| hasher | It is the second template parameter (Hash) | defaults to: hash |
| key_equal | It is the third template parameter (Pred) | defaults to: equal_to |
| allocator_type | It is the fourth template parameter (Alloc) | defaults to: allocator |
| reference | Alloc::reference | |
| const_reference | Alloc::const_reference | |
| pointer | Alloc::pointer | for the default allocator: value_type* |
| const_pointer | Alloc::const_pointer | for the default allocator: const value_type* |
| iterator | a forward iterator to const value_type | * convertible to const_iterator |
| const_iterator | a forward iterator to const value_type | * |
| local_iterator | a forward iterator to const value_type | * convertible to const_local_iterator |
| const_local_iterator | a forward iterator to const value_type | * |
| size_type | an unsigned integral type | usually the same as size_t |
| difference_type | a signed integral type | usually the same as ptrdiff_t |
以下是成员函数列表
| Sr.No. | Method & Description |
|---|---|
| 1 | (constructor)
It constructs unordered_set. |
| 2 | (destructor)
It destroys unordered_set. |
| 3 | operator=
It is used to assign the content. |
| Sr.No. | Capacity & Description |
|---|---|
| 1 | empty
It is used to test whether container is empty. |
| 2 | size
It returns container size. |
| 3 | max_size
It returns maximum size. |
| Sr.No. | Iterators & Description |
|---|---|
| 1 | begin
It returns iterator to beginning. |
| 2 | end
It returns iterator to end. |
| 3 | cbegin
It returns const_iterator to beginning. |
| 4 | cend
It return const_iterator to end. |
| Sr.No. | Element lookup & Description |
|---|---|
| 1 | find
It is used to get iterator to element. |
| 2 | count
It is used to count elements with a specific key. |
| 3 | equal_range
It is used to get range of elements with a specific key. |
| Sr.No. | Modifiers & Description |
|---|---|
| 1 | emplace
It is used to construct and insert element. |
| 2 | emplace_hint
It is used to construct and insert element with hint. |
| 3 | insert
It is used to insert elements. |
| 4 | erase
It is used to erase elements. |
| 5 | clear
It is used to clear content. |
| 6 | swap
It is used to swap content. |
| Sr.No. | Buckets & Description |
|---|---|
| 1 | bucket_count
It returns number of buckets. |
| 2 | max_bucket_count
It returns maximum number of buckets. |
| 3 | bucket_size
It returns bucket size. |
| 4 | bucket
It locates element’s bucket. |
| Sr.No. | Hash policy & Description |
|---|---|
| 1 | load_factor It returns load factor. |
| 2 | max_load_factor
It is used to get or set maximum load factor. |
| 3 | rehash
It is used to set number of buckets. |
| 4 | reserve It gives a request to capacity chage of backets |
| Sr.No. | Observers & Description |
|---|---|
| 1 | hash_function It is used to get hash function. |
| 2 | key_eq
It is used to get key equivalence predicate. |
| 3 | get_allocator
It is used to get allocator. |
| Sr.No. | Non-member function overloads & Description |
|---|---|
| 1 | operators (unordered_set)
It is used to get hash function. |
| 2 | swap (unordered_set)
It exchanges contents of two unordered_set containers. |
| Sr.No. | Non-member function overloads & Description |
|---|---|
| 1 | operators (unordered_set)
It is used to get hash function. |
| 2 | swap (unordered_set)
It exchanges contents of two unordered_set containers. |