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Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
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`boost::unordered_map` — An unordered associative container that associates unique keys with another value.
`boost::unordered_map` — 一个无序关联容器，用于将唯一的键与另一个值关联起来。
Synopsis
概要
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---
---
Description
描述
*Template Parameters*
*模板参数*
_Key_
_键_
`Key` must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the container (i.e. `allocator_traits` can destroy it).
`Key` 必须可以从容器中 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^]（即 `allocator_traits` 能够销毁它）。
_T_
_T_
`T` must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the container (i.e. `allocator_traits` can destroy it).
`T` 必须可以从容器中 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^]（即 `allocator_traits` 可以销毁它）。
_Hash_
_Hash_
A unary function object type that acts a hash function for a `Key`. It takes a single argument of type `Key` and returns a value of type `std::size_t`.
一种一元函数对象类型，用作 `Key` 的哈希函数。它接受一个 `Key` 类型的参数，并返回一个 `std::size_t` 类型的值。
_Pred_
_Pred_
A binary function object that implements an equivalence relation on values of type `Key`. A binary function object that induces an equivalence relation on values of type `Key`. It takes two arguments of type `Key` and returns a value of type bool.
一种二元函数对象，用于实现 `Key` 类型值上的等价关系。它接受两个 `Key` 类型的参数，并返回一个 `bool` 类型的值。
_Allocator_
_Allocator_
An allocator whose value type is the same as the container's value type.
一种分配器，其值类型与容器的值类型相同。
Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
支持使https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[异形指针] 的分配器。
The elements are organized into buckets. Keys with the same hash code are stored in the same bucket.
元素被组织到桶中。具有相同哈希码的键存储在同一桶中。
The number of buckets can be automatically increased by a call to insert, or as the result of calling rehash.
桶的数量可以通过调用 insert 自动增加，或者作为调用 rehash 的结果。
Configuration macros
配置宏
`BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0`
`BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0`
Globally define this macro to support loading of ``unordered_map``s saved to a Boost.Serialization archive with a version of Boost prior to Boost 1.84.
全局定义此宏以支持加载由 Boost 1.84 之前版本的 Boost 保存到 Boost.Serialization 归档中的 `unordered_map`。
Typedefs
类型定义
An iterator whose value type is `value_type`.
一个迭代器，其值类型为 `value_type`。
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The iterator category is at least a forward iterator.
迭代器类别至少为前向迭代器。
Convertible to `const_iterator`.
可转换为 `const_iterator` 。
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---
A constant iterator whose value type is `value_type`.
一个常量迭代器，其值类型为 `value_type` 。
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The iterator category is at least a forward iterator.
迭代器类别至少为前向迭代器。
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---
---
An iterator with the same value type, difference type and pointer and reference type as iterator.
一种迭代器，其值类型、差值类型以及指针和引用类型均与 iterator 相同。
A `local_iterator` object can be used to iterate through a single bucket.
`local_iterator` 对象可用于遍历单个桶内的元素。
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Returns:;; The average number of elements per bucket.
返回：;; 每个桶的平均元素个数。
max_load_factor
max_load_factor
```c++ float max_load_factor() const noexcept; ```
```c++ float max_load_factor() const noexcept; ```
Returns:;; Returns the current maximum load factor.
返回：;; 返回当前的最大负载因子。
rehash
重哈希
```c++ void rehash(size_type n); ```
```c++ void rehash(size_type n); ```
Changes the number of buckets so that there are at least `n` buckets, and so that the load factor is less than or equal to the maximum load factor. When applicable, this will either grow or shrink the `bucket_count()` associated with the container.
改变桶的数量，使得至少包含 `n` 个桶，并且使得负载因子小于或等于最大负载因子。在适用的情况下，这将增大或缩小与容器相关联的 `bucket_count()`。
When `size() == 0`, `rehash(0)` will deallocate the underlying buckets array.
当 `size() == 0` 时，`rehash(0)` 将释放底层桶数组的内存。
reserve
保留
operator
operator
Return `true` if `x.size() == y.size()` and for every element in `x`, there is an element in `y` with the same key, with an equal value (using `operator==` to compare the value types).
如果 `x.size() == y.size()` 并且对于 `x` 中的每个元素，在 `y` 中都有一个具有相同键且值相等的元素（使用 `operator==` 比较值类型），则返回 `true`。
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, `a` as the allocator and a maximum load factor of `1.0` and inserts the elements from `il` into it.
构造一个至少包含 n 个桶的空容器，使用 hf 作为哈希函数，eql 作为键相等谓词，a 作为分配器，以及最大负载因子 1.0，并将 il 中的元素插入其中。
Bucket Count Constructor with Hasher and Allocator
带哈希函数和分配器的桶数构造函数
```c++ unordered_map(size_type n, hasher const& hf, allocator_type const& a); ```
```c++ unordered_map(size_type n, hasher const& hf, allocator_type const& a); ```
An allocator whose value type is the same as the container's value type.
一种分配器，其值类型与容器的值类型相同。
Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
支持使https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[异形指针] 的分配器。
A const_local_iterator object can be used to iterate through a single bucket.
`const_local_iterator` 对象可用于遍历单个桶。
Constructs an empty container using `hasher()` as the hash function, `key_equal()` as the key equality predicate, `allocator_type()` as the allocator and a maximum load factor of `1.0`.
使用 `hasher()` 作为哈希函数，`key_equal()` 作为键相等谓词，`allocator_type()` 作为分配器，以及最大负载因子 `1.0` 构造一个空容器。
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, `a` as the allocator and a maximum load factor of `1.0`.
构造一个至少包含 `n` 个桶的空容器，使用 `hf` 作为哈希函数，`eql` 作为键相等谓词，`a` 作为分配器，以及最大负载因子 `1.0`。
Iterator Range Constructor
迭代器范围构造函数
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, `a` as the allocator and a maximum load factor of `1.0` and inserts the elements from `[f, l)` into it.
构造一个至少包含 `n` 个桶的空容器，使用 `hf` 作为哈希函数，`eql` 作为键相等谓词，`a` 作为分配器，以及最大负载因子 `1.0`，并将 `[f, l)` 范围内的元素插入其中。
Copy Constructor
复制构造函数
If `Allocator::select_on_container_copy_construction` exists and has the right signature, the allocator will be constructed from its result.
如果 `Allocator::select_on_container_copy_construction` 存在且具有正确的签名，则分配器将根据其结果进行构造。
Move Constructor
移动构造函数
```c++ unordered_map(unordered_map&& other); ```
```c++ unordered_map(unordered_map&& other); ```
The move constructor.
移动构造函数。
Notes:;; This is implemented using Boost.Move. Requires:;; `value_type` is move-constructible.
注意：此函数使用 Boost.Move 实现。
要求：`value_type` 可移动构造。
```c++ template<class InputIterator> unordered_map(InputIterator f, InputIterator l, const allocator_type& a); ```
```c++ template<class inputiterator=""> unordered_map(InputIterator f, InputIterator l, const allocator_type&amp; a); ```</class>
Constructs an empty container using `a` as the allocator, with the default hash function and key equality predicate and a maximum load factor of `1.0` and inserts the elements from `[f, l)` into it.
使用 `a` 作为分配器，以默认哈希函数、默认键相等谓词和最大负载因子 `1.0` 构造一个空容器，并将 `[f, l)` 范围内的元素插入其中。
Copy Constructor with Allocator
带分配器的复制构造函数

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Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
Allocators using 支持使https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.异形指针] 的分配器。
06/05/2026
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Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
06/05/2026
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safe-html, strict-same
Unit identifier
55400
Source string location
:303
String age
06/05/2026
Last updated
06/06/2026
Source string age
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doc/modules/ROOT/pages/reference/unordered_map_zh_Hans.adoc, string 18