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Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
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:1711
Notes:;; Behavior is undefined if the two containers don't have equivalent equality predicates.
备注：;; 如果两个容器不具有等价的相等谓词，则行为未定义。
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---
---
operator!
operator!
```c++ template<class Key, class T, class Hash, class Pred, class Alloc> bool operator!=(const unordered_map<Key, T, Hash, Pred, Alloc>& x, const unordered_map<Key, T, Hash, Pred, Alloc>& y); ```
```c++ template<class key,="" class="" t,="" hash,="" pred,="" alloc=""> bool operator!=(const unordered_map<key, t,="" hash,="" pred,="" alloc="">&amp; x, const unordered_map<key, t,="" hash,="" pred,="" alloc="">&amp; y); ```</key,></key,></class>
Return `false` 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 `false`。
:1725
Notes:;; Behavior is undefined if the two containers don't have equivalent equality predicates.
备注：;; 如果两个容器不具有等价的相等谓词，则行为未定义。
Swap
交换
```c++ template<class Key, class T, class Hash, class Pred, class Alloc> void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x, unordered_map<Key, T, Hash, Pred, Alloc>& y) noexcept(noexcept(x.swap(y))); ```
```c++ template<class key,="" class="" t,="" hash,="" pred,="" alloc=""> void swap(unordered_map<key, t,="" hash,="" pred,="" alloc="">&amp; x, unordered_map<key, t,="" hash,="" pred,="" alloc="">&amp; y) noexcept(noexcept(x.swap(y))); ```</key,></key,></class>
Swaps the contents of `x` and `y`.
交换 `x` 和 `y` 的内容。
:1737
If `Allocator::propagate_on_container_swap` is declared and `Allocator::propagate_on_container_swap::value` is `true` then the containers' allocators are swapped. Otherwise, swapping with unequal allocators results in undefined behavior.
如果 `Allocator::propagate_on_container_swap` 已声明且 `Allocator::propagate_on_container_swap::value` 为 `true`，则交换两个容器的分配器。否则，使用不相等的分配器进行交换将导致未定义行为。
Effects:;; `x.swap(y)` Throws:;; Doesn't throw an exception unless it is thrown by the copy constructor or copy assignment operator of `key_equal` or `hasher`. Notes:;; The exception specifications aren't quite the same as the C++11 standard, as the equality predicate and hash function are swapped using their copy constructors.
效果：;; `x.swap(y)`
抛出：;; 除非由 `key_equal` 或 `hasher` 的复制构造函数或复制赋值运算符抛出异常，否则不会抛出异常。
备注：;; 异常规范与 C++11 标准不完全相同，因为相等谓词和哈希函数是通过它们的复制构造函数进行交换的。
:1744
---
---
erase_if
erase_if
```c++ template<class K, class T, class H, class P, class A, class Predicate> typename unordered_map<K, T, H, P, A>::size_type erase_if(unordered_map<K, T, H, P, A>& c, Predicate pred); ```
```c++ template<class k,="" class="" t,="" h,="" p,="" a,="" predicate=""> typename unordered_map<k, t,="" h,="" p,="" a="">::size_type erase_if(unordered_map<k, t,="" h,="" p,="" a="">&amp; c, Predicate pred); ```</k,></k,></class>
Traverses the container `c` and removes all elements for which the supplied predicate returns `true`.
遍历容器 `c` 并移除所有使给定谓词返回 `true` 的元素。
Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
返回：;; 被移除的元素数量。备注：;; 等价于：```c++auto original_size = c.size();for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; }}return original_size - c.size();```注意，传递给 `pred` 的引用是非常量的。
Serialization
序列化
``unordered_map``s can be archived/retrieved by means of link:../../../../../serialization/index.html[Boost.Serialization^] using the API provided by this library. Both regular and XML archives are supported.
`unordered_map` 可以通过本库提供的 API，使用 link:../../../../../serialization/index.html[Boost.Serialization^] 进行归档/恢复。支持常规归档和 XML 归档。
Saving an unordered_map to an archive
将 unordered_map 保存到归档
Saves all the elements of an `unordered_map` `x` to an archive (XML archive) `ar`.
将 `unordered_map` `x` 的所有元素保存到归档（XML 归档）`ar` 中。
Requires:;; `std::remove_const<key_type>::type` and `std::remove_const<mapped_type>::type` are serializable (XML serializable), and they do support Boost.Serialization `save_construct_data`/`load_construct_data` protocol (automatically suported by https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^] types).
要求：;; `std::remove_const<key_type>::type` 和 `std::remove_const<mapped_type>::type` 必须是可序列化的（支持 XML 序列化），并且它们支持 Boost.Serialization 的 `save_construct_data`/`load_construct_data` 协议（该协议由 https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^] 类型的自动支持）。</mapped_type></key_type>
:1790
---
---
Loading an unordered_map from an archive
从归档中加载 unordered_map
Deletes all preexisting elements of an `unordered_map` `x` and inserts from an archive (XML archive) `ar` restored copies of the elements of the original `unordered_map` `other` saved to the storage read by `ar`.
删除 `unordered_map` `x` 中所有已存在的元素，并从归档（XML 归档）`ar` 中插入由 `ar` 所读取存储中保存的原始 `unordered_map` `other` 元素的恢复副本。
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] from `(std::remove_const<key_type>::type&&, std::remove_const<mapped_type>::type&&)`. `x.key_equal()` is functionally equivalent to `other.key_equal()`. Note:;; If the archive was saved using a release of Boost prior to Boost 1.84, the configuration macro `BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0` has to be globally defined for this operation to succeed; otherwise, an exception is thrown.
要求：;; `value_type` 可以从 `(std::remove_const<key_type>::type&amp;&amp;, std::remove_const<mapped_type>::type&amp;&amp;)` 进行 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^]。`x.key_equal()` 在功能上等价于 `other.key_equal()`。
注意：;; 如果归档是使用 Boost 1.84 之前的 Boost 版本保存的，则必须全局定义配置宏 `BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0` 才能使此操作成功；否则将抛出异常。</mapped_type></key_type>
:1806
---
---
Saving an iterator/const_iterator to an archive
将迭代器/常量迭代器保存到归档中
Saves the positional information of an `iterator` (`const_iterator`) `it` to an archive (XML archive) `ar`. `it` can be and `end()` iterator.
将 `iterator`（`const_iterator`）`it` 的位置信息保存到归档（XML 归档）`ar` 中。`it` 可以是 `end()` 迭代器。
Requires:;; The `unordered_map` `x` pointed to by `it` has been previously saved to `ar`, and no modifying operations have been issued on `x` between saving of `x` and saving of `it`.
要求：;; `it` 所指向的 `unordered_map` `x` 此前已保存至 `ar`，并且在保存 `x` 和保存 `it` 之间未对 `x` 执行任何修改操作。
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---
---
Loading an iterator/const_iterator from an archive
从归档中加载迭代器/常量迭代器
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swap
交换
```c++ iterator find(const key_type& k); const_iterator find(const key_type& k) const; template<class K> iterator find(const K& k); template<class K> const_iterator find(const K& k) const; template<typename CompatibleKey, typename CompatibleHash, typename CompatiblePredicate> iterator find(CompatibleKey const& k, CompatibleHash const& hash, CompatiblePredicate const& eq); template<typename CompatibleKey, typename CompatibleHash, typename CompatiblePredicate> const_iterator find(CompatibleKey const& k, CompatibleHash const& hash, CompatiblePredicate const& eq) const;
```c++ iterator find(const key_type&amp; k); const_iterator find(const key_type&amp; k) const; template<class k=""> iterator find(const K&amp; k); template<class k=""> const_iterator find(const K&amp; k) const; template<typename compatiblekey,="" typename="" compatiblehash,="" compatiblepredicate=""> iterator find(CompatibleKey const&amp; k, CompatibleHash const&amp; hash, CompatiblePredicate const&amp; eq); template<typename compatiblekey,="" typename="" compatiblehash,="" compatiblepredicate=""> const_iterator find(CompatibleKey const&amp; k, CompatibleHash const&amp; hash, CompatiblePredicate const&amp; eq) const;</typename></typename></class></class>
Returns:;; The number of elements with key equivalent to `k`. Notes:;; The `template<class K>` overload only participates in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回：;; 键与 `k` 等价的元素个数。
备注：;; 仅当 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef 时，`template<class k="">` 重载才会参与重载决议。库假定 `Hash` 可同时以 `K` 和 `Key` 类型调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型的开销。</class>
equal_range
equal_range
```c++ size_type max_bucket_count() const noexcept; ```
```c++ size_type max_bucket_count() const noexcept; ```
```c++ unordered_map(std::initializer_list<value_type> il, const allocator_type& a); ```
```c++ unordered_map(std::initializer_list<value_type> il, const allocator_type&amp; a); ```</value_type>
Returns:;; A range containing all elements with key equivalent to `k`. If the container doesn't contain any such elements, returns `std::make_pair(b.end(), b.end())`. Notes:;; The `template<class K>` overloads only participate in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回：;; 一个范围，包含所有键与 `k` 等价的元素。若容器中不包含任何此类元素，则返回 `std::make_pair(b.end(), b.end())`。
备注：;; 仅当 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef 时，`template<class k="">` 重载才会参与重载决议。库假定 `Hash` 可同时以 `K` 和 `Key` 类型调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型的开销。</class>
operator++[++++]++
operator++[++++]++
Returns:;; A reference to `x.second` where `x` is the (unique) element whose key is equivalent to `k`. Throws:;; An exception object of type `std::out_of_range` if no such element is present. Notes:;; The `template<class K>` overloads only participate in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回：;; 指向 `x.second` 的引用，其中 `x` 是键与 `k` 等价的（唯一）元素。
抛出：;; 如果不存在这样的元素，则抛出 `std::out_of_range` 类型的异常对象。
备注：;; 仅当 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef 时，`template<class k="">` 重载才会参与重载决议。库假定 `Hash` 可同时以 `K` 和 `Key` 类型调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型的开销。</class>
```c++ unordered_map(std::initializer_list<value_type> il, size_type n, const allocator_type& a); ```
```c++ unordered_map(std::initializer_list<value_type> il, size_type n, const allocator_type&amp; a); ```</value_type>
initializer_list Constructor with Bucket Count and Hasher and Allocator
带桶数、哈希函数和分配器的初始化列表构造函数
```c++ unordered_map(std::initializer_list<value_type> il, size_type n, const hasher& hf, const allocator_type& a); ```
```c++ unordered_map(std::initializer_list<value_type> il, size_type n, const hasher&amp; hf, const allocator_type&amp; a); ```</value_type>
```c++ local_iterator begin(size_type n); const_local_iterator begin(size_type n) const; ```
```c++ local_iterator begin(size_type n); const_local_iterator begin(size_type n) const; ```
- It has an `InputIterator` template parameter and a type that does not qualify as an input iterator is deduced for that parameter. - It has an `Allocator` template parameter and a type that does not qualify as an allocator is deduced for that parameter. - It has a `Hash` template parameter and an integral type or a type that qualifies as an allocator is deduced for that parameter. - It has a `Pred` template parameter and a type that qualifies as an allocator is deduced for that parameter.
- 它具有 `InputIterator` 模板参数，并且为该参数推导出的类型不符合输入迭代器的要求。
- 它具有 `Allocator` 模板参数，并且为该参数推导出的类型不符合分配器的要求。
- 它具有 `Hash` 模板参数，并且为该参数推导出的是整数类型或符合分配器要求的类型。
- 它具有 `Pred` 模板参数，并且为该参数推导出的是符合分配器要求的类型。
__iter-key-type__
__iter-key-type__
Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
返回：;; 被移除的元素数量。备注：;; 等价于：```c++auto original_size = c.size();for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; }}return original_size - c.size();```注意，传递给 `pred` 的引用是非常量的。
``unordered_map``s can be archived/retrieved by means of link:../../../../../serialization/index.html[Boost.Serialization^] using the API provided by this library. Both regular and XML archives are supported.
`unordered_map` 可以通过本库提供的 API，使用 link:../../../../../serialization/index.html[Boost.Serialization^] 进行归档/恢复。支持常规归档和 XML 归档。
Requires:;; `std::remove_const<key_type>::type` and `std::remove_const<mapped_type>::type` are serializable (XML serializable), and they do support Boost.Serialization `save_construct_data`/`load_construct_data` protocol (automatically suported by https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^] types).
要求：;; `std::remove_const<key_type>::type` 和 `std::remove_const<mapped_type>::type` 必须是可序列化的（支持 XML 序列化），并且它们支持 Boost.Serialization 的 `save_construct_data`/`load_construct_data` 协议（该协议由 https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^] 类型的自动支持）。</mapped_type></key_type>
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `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，a 作为分配器，最大负载因子为 1.0，并将 il 中的元素插入其中。
Destructor
析构函数
```c++ ~unordered_map(); ```
```c++ ~unordered_map(); ```
Note:;; The destructor is applied to every element, and all memory is deallocated
注意：析构函数会应用于每个元素，并且所有内存都会被释放。
Assignment
赋值操作
Copy Assignment
复制赋值
The assignment operator. Copies the contained elements, hash function, predicate and maximum load factor but not the allocator.
赋值运算符。拷贝所包含的元素、哈希函数、谓词和最大负载因子，但不拷贝分配器。
If `Alloc::propagate_on_container_copy_assignment` exists and `Alloc::propagate_on_container_copy_assignment::value` is `true`, the allocator is overwritten, if not the copied elements are created using the existing allocator.
如果 `Alloc::propagate_on_container_copy_assignment` 存在且 `Alloc::propagate_on_container_copy_assignment::value` 为 `true`，则分配器会被覆盖；否则，拷贝的元素将使用现有的分配器创建。
Move Assignment
移动赋值
```c++ unordered_map& operator=(unordered_map&& other) noexcept(boost::allocator_traits<Allocator>::is_always_equal::value && boost::is_nothrow_move_assignable_v<Hash> && boost::is_nothrow_move_assignable_v<Pred>); ``` The move assignment operator.
```c++ unordered_map&amp; operator=(unordered_map&amp;&amp; other) noexcept(boost::allocator_traits<allocator>::is_always_equal::value &amp;&amp; boost::is_nothrow_move_assignable_v<hash> &amp;&amp; boost::is_nothrow_move_assignable_v<pred>); ``` The move assignment operator.</pred></hash></allocator>
Makes an `iterator` (`const_iterator`) `it` point to the restored position of the original `iterator` (`const_iterator`) saved to the storage read by an archive (XML archive) `ar`.
使 `iterator`（`const_iterator`）`it` 指向保存到由归档（XML 归档）`ar` 读取的存储中的原始 `iterator`（`const_iterator`）的被恢复位置。
Requires:;; If `x` is the `unordered_map` `it` points to, no modifying operations have been issued on `x` between loading of `x` and loading of `it`.
要求：;; 如果 `x` 是 `it` 所指向的 `unordered_map`，则在加载 `x` 和加载 `it` 之间未对 `x` 执行任何修改操作。

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Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
Returns:;; The number of erased elements. Notes:;; Equivalent to: + + 返回：;; 被移除的元素数量。备注：;; 等价于：```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } ++i; }}return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.注意，传递给 `pred` 的引用是非常量的。
06/05/2026
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Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
Returns:;; The number of erased elements. Notes:;; Equivalent to: + + ```c++ auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size(); ``` + Note that the references passed to `pred` are non-const.
06/05/2026
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