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Saves all the elements of an `unordered_map` `x` to an archive (XML archive) `ar`.
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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`。
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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。
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---
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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>
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---
---
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
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。
English Chinese (Simplified Han script) Actions
Deduction Guides
推导指引
A deduction guide will not participate in overload resolution if any of the following are true:
在以下任一条件成立时，推导指引将不参与重载决议：
A `size_­type` parameter type in a deduction guide refers to the `size_­type` member type of the container type deduced by the deduction guide. Its default value coincides with the default value of the constructor selected.
推导指引中的 `size_type` 参数类型指向由该推导指引所推导出的容器类型的 `size_type` 成员类型。其默认值与所选构造函数的默认值一致。
__iter-to-alloc-type__
__iter-to-alloc-type__
Equality Comparisons
相等性比较
```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>
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>
```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>
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。
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。
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。
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, the default 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，使用默认的键相等谓词，a 作为分配器，以及最大负载因子 1.0。
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>
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。
initializer_list Constructor with Allocator
带分配器的初始化列表构造函数
Constructs an empty container using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
使用 a 作为分配器，最大负载因子为 1.0，构造一个空容器，并将 il 中的元素插入其中。
```c++ unordered_map& operator=(unordered_map const& other); ```
```c++ unordered_map&amp; operator=(unordered_map const&amp; other); ```
```c++ iterator end() noexcept; const_iterator end() const noexcept; ```
```c++ iterator end() noexcept; const_iterator end() const noexcept; ```
Returns:;; An iterator which refers to the past-the-end value for the container.
返回：指向容器尾后值的迭代器。
```c++ const_iterator cbegin() const noexcept; ```
```c++ const_iterator cbegin() const noexcept; ```
Returns:;; A `const_iterator` referring to the first element of the container, or if the container is empty the past-the-end value for the container.
返回：指向容器第一个元素的 `const_iterator`，如果容器为空则返回容器的尾后值。
__iter-mapped-type__
__iter-mapped-type__
```c++ size_type size() const noexcept; ```
```c++ size_type size() const noexcept; ```
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into `X` from `args`. Returns:;; The bool component of the return type is true if an insert took place. + + If an insert took place, then the iterator points to the newly inserted element. Otherwise, it points to the element with equivalent key. Throws:;; If an exception is thrown by an operation other than a call to `hasher` the function has no effect. Notes:;; Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor. + + Pointers and references to elements are never invalidated. + + If `args...` is of the form `k,v`, it delays constructing the whole object until it is certain that an element should be inserted, using only the `k` argument to check. This optimization happens when the map's `key_type` is move constructible or when the `k` argument is a `key_type`.
要求：`value_type` 必须可以从 `args` 出发在 `X` 中进行 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[可原位构造^]。 返回：如果发生了插入，则返回类型的 bool 分量为 true。
如果发生了插入，则迭代器指向新插入的元素；否则，指向具有等价键的元素。
抛出：如果除调用 `hasher` 之外的操作抛出异常，则该函数无效果。
注意：可能使迭代器失效，但仅当插入导致负载因子大于或等于最大负载因子时才会发生。 指向元素的指针和引用永远不会失效。
如果 `args...` 的形式为 `k,v`，则该函数会延迟构造整个对象，直到确定应该插入元素为止，仅使用 `k` 参数进行检查。当映射的 `key_type` 可移动构造或 `k` 参数本身就是 `key_type` 类型时，此优化生效。
Returns:;; The index of the bucket which would contain an element with key `k`. Postconditions:;; The return value is less than `bucket_count()`. 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：;; 包含键 `k` 的元素的桶索引。
后置条件：;; 返回值小于 `bucket_count()`。
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>

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Saves all the elements of an `unordered_map` `x` to an archive (XML archive) `ar`.
Saves all the elements of an `unordered_map` `x` to an archive (XML archive) 将 `unordered_map` `x` 的所有元素保存到归档（XML 归档）`ar`. 中。
06/05/2026
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String added in the repository
Saves all the elements of an `unordered_map` `x` to an archive (XML archive) `ar`.
Saves all the elements of an `unordered_map` `x` to an archive (XML archive) `ar`.
06/05/2026
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Glossary

English Chinese (Simplified Han script)
No related strings found in the glossary.

String information

Flags
safe-html, strict-same
Unit identifier
55858
Source string location
:1781
String age
06/05/2026
Last updated
06/06/2026
Source string age
06/05/2026
Translation file AsciiDoc file
doc/modules/ROOT/pages/reference/unordered_map_zh_Hans.adoc, string 476