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In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
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[#regular] = Regular Containers
[#regular] = 常规容器
:idprefix: regular_
:idprefix: regular_
Boost.Unordered closed-addressing containers (`boost::unordered_set`, `boost::unordered_map`, `boost::unordered_multiset` and `boost::unordered_multimap`) are fully conformant with the C++ specification for unordered associative containers, so for those who know how to use `std::unordered_set`, `std::unordered_map`, etc., their homonyms in Boost.Unordered are drop-in replacements. The interface of open-addressing containers (`boost::unordered_node_set`, `boost::unordered_node_map`, `boost::unordered_flat_set` and `boost::unordered_flat_map`) is very similar, but they present some minor differences listed in the dedicated xref:compliance.adoc#compliance_open_addressing_containers[standard compliance section].
Boost.Unordered 的闭寻址容器（ `boost::unordered++_++set` 、 `boost::unordered++_++map` 、 `boost::unordered++_++multiset` 与 `boost::unordered++_++multimap` ）完全符合 C{plus}{plus} 无序关联容器的标准规范。因此，对于熟悉 `std::unordered++_++set` 、 `std::unordered++_++map` 等用法的用户，可直接将其替换为Boost.Unordered 中的同名容器。开放寻址容器（ `boost::unordered++_++node++_++set` 、 `boost::unordered++_++node++_++map` 、 `boost::unordered++_++flat++_++set` 和 `boost::unordered++_++flat++_++map` ）的接口与之高度相似，但存在一些细微差异，详见专门的 xref:compliance.adoc#compliance_open_addressing_containers[标准符合性章节] 。
For readers without previous experience with hash containers but familiar with normal associative containers (`std::set`, `std::map`, `std::multiset` and `std::multimap`), Boost.Unordered containers are used in a similar manner:
对于没有哈希容器经验但熟悉常规关联容器（ `std::set` 、 `std::map` 、 `std::multiset` 和 `std::multimap` ）的读者，Boost.Unordered 容器的使用方式与之类似：
But since the elements aren't ordered, the output of:
但由于元素不按顺序存储，以下代码的输出结果：
can be in any order. For example, it might be:
可能以任意顺序输出。例如，结果可能为：
There are other differences, which are listed in the xref:regular.adoc#comparison[Comparison with Associative Containers] section.
其他差异列于 xref:regular.adoc#comparison[与关联容器的对比] 章节中。
Iterator Invalidation
迭代器失效
It is not specified how member functions other than `rehash` and `reserve` affect the bucket count, although `insert` can only invalidate iterators when the insertion causes the container's load to be greater than the maximum allowed. For most implementations this means that `insert` will only change the number of buckets when this happens. Iterators can be invalidated by calls to `insert`, `rehash` and `reserve`.
标准未明确规定除 `rehash` 和 `reserve` 之外的成员函数如何影响桶数量，但 `insert` 操作仅当导致容器负载超过最大允许值时才会使迭代器失效。在大多数实现中，这意味着 `insert` 仅在此种情况下才会改变桶的数量。迭代器可能因调用 `insert` 、 `rehash` 或 `reserve` 而失效。
As for pointers and references, they are never invalidated for node-based containers (`boost::unordered_[multi]set`, `boost::unordered_[multi]map`, `boost::unordered_node_set`, `boost::unordered_node_map`), but they will be when rehashing occurs for `boost::unordered_flat_set` and `boost::unordered_flat_map`: this is because these containers store elements directly into their holding buckets, so when allocating a new bucket array the elements must be transferred by means of move construction.
对于基于节点的容器（ `boost::unordered++_[++multi++]++set` 、 `boost::unordered++_[++multi++]++map` 、 `boost::unordered++_++node++_++set` 、 `boost::unordered++_++node++_++map` ），其指针和引用永远不会失效。但对于 `boost::unordered++_++flat++_++set` 和 `boost::unordered++_++flat++_++map` ，在发生重哈希时指针和引用将会失效：这是因为这些容器将元素直接存储在桶中，当分配新的桶数组时，必须通过移动构造来转移元素。
In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
与为 `vector` 使用 `reserve` 类似，在插入大量元素之前调用 `reserve` 是一个好主意。这样可以避免代价高昂的重哈希操作，并且让你能够存储迭代器，确信它们不会被失效。如果你要向容器 `x` 插入 `n` 个元素，可以先调用：
``` x.reserve(n); ```
``` x.reserve(n); ```
`reserve(n)` reserves space for at least `n` elements, allocating enough buckets
`reserve(n)` 为至少 `n` 个元素预留空间，分配足够数量的桶，
so as to not exceed the maximum load factor. + Because the maximum load factor is defined as the number of elements divided by the total number of available buckets, this function is logically equivalent to: + ``` x.rehash(std::ceil(n / x.max_load_factor())) ``` + See the xref:reference/unordered_map.adoc#unordered_map_rehash[reference for more details] on the `rehash` function.
以确保不超过最大负载因子。由于最大负载因子定义为元素数量除以可用桶的总数，该函数在逻辑上等价于：
```cppx.rehash(std::ceil(n / x.max_load_factor()))```
有关 `rehash` 函数的更多详细信息，请参阅 xref:reference/unordered_map.adoc#unordered_map_rehash[参考文档]。
:idprefix: comparison_
:idprefix: comparison_
Comparison with Associative Containers
与关联容器的对比
:100
Associative Containers
关联容器
:100
Unordered Associative Containers
无序关联容器
Parameterized by an ordering relation `Compare`
通过排序关系 `Compare` 进行 参数化
Parameterized by a function object `Hash` and an equivalence relation `Pred`
由函数对象`哈希对象`和等价关系`谓词对象`参数化。
Keys can be compared using `key_compare` which is accessed by member function `key_comp()`, values can be compared using `value_compare` which is accessed by member function `value_comp()`.
键可通过成员函数`key_comp()`获取的`键比较对象`进行比较，值可通过成员函数`value_comp()`获取的`值比较对象`进行比较。
Keys can be hashed using `hasher` which is accessed by member function `hash_function()`, and checked for equality using `key_equal` which is accessed by member function `key_eq()`. There is no function object for compared or hashing values.
键可通过成员函数`hash_function()`获取的`哈希对象`进行哈希计算，并通过成员函数`key_eq()`获取的`键相等比较对象`检查是否相等。不存在用于值比较或值哈希的函数对象。
Constructors have optional extra parameters for the comparison object.
构造函数包含用于比较对象的可选额外参数。
Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
构造函数包含可选的额外参数，用于指定初始最小哈希桶数量、哈希函数以及相等性判断对象。
Keys `k1`, `k2` are considered equivalent if `!Compare(k1, k2) && !Compare(k2, k1)`.
若`!对象(k1, k2) && !对象(k2, k1)`，则键`k1`、`k2`视为等价。
Keys `k1`, `k2` are considered equivalent if `Pred(k1, k2)`
若`谓词对象(k1, k2)成立`，则键`k1`、`k2`视为等价。
English Chinese (Simplified Han script) Actions
[#regular] = Regular Containers
[#regular] = 常规容器
Erase by key, `k`
按键`k`移除
:idprefix: comparison_
:idprefix: comparison_
constant
常数级
Boost.Unordered closed-addressing containers (`boost::unordered_set`, `boost::unordered_map`, `boost::unordered_multiset` and `boost::unordered_multimap`) are fully conformant with the C++ specification for unordered associative containers, so for those who know how to use `std::unordered_set`, `std::unordered_map`, etc., their homonyms in Boost.Unordered are drop-in replacements. The interface of open-addressing containers (`boost::unordered_node_set`, `boost::unordered_node_map`, `boost::unordered_flat_set` and `boost::unordered_flat_map`) is very similar, but they present some minor differences listed in the dedicated xref:compliance.adoc#compliance_open_addressing_containers[standard compliance section].
Boost.Unordered 的闭寻址容器（ `boost::unordered++_++set` 、 `boost::unordered++_++map` 、 `boost::unordered++_++multiset` 与 `boost::unordered++_++multimap` ）完全符合 C{plus}{plus} 无序关联容器的标准规范。因此，对于熟悉 `std::unordered++_++set` 、 `std::unordered++_++map` 等用法的用户，可直接将其替换为Boost.Unordered 中的同名容器。开放寻址容器（ `boost::unordered++_++node++_++set` 、 `boost::unordered++_++node++_++map` 、 `boost::unordered++_++flat++_++set` 和 `boost::unordered++_++flat++_++map` ）的接口与之高度相似，但存在一些细微差异，详见专门的 xref:compliance.adoc#compliance_open_addressing_containers[标准符合性章节] 。
For readers without previous experience with hash containers but familiar with normal associative containers (`std::set`, `std::map`, `std::multiset` and `std::multimap`), Boost.Unordered containers are used in a similar manner:
对于没有哈希容器经验但熟悉常规关联容器（ `std::set` 、 `std::map` 、 `std::multiset` 和 `std::multimap` ）的读者，Boost.Unordered 容器的使用方式与之类似：
But since the elements aren't ordered, the output of:
但由于元素不按顺序存储，以下代码的输出结果：
can be in any order. For example, it might be:
可能以任意顺序输出。例如，结果可能为：
As for pointers and references, they are never invalidated for node-based containers (`boost::unordered_[multi]set`, `boost::unordered_[multi]map`, `boost::unordered_node_set`, `boost::unordered_node_map`), but they will be when rehashing occurs for `boost::unordered_flat_set` and `boost::unordered_flat_map`: this is because these containers store elements directly into their holding buckets, so when allocating a new bucket array the elements must be transferred by means of move construction.
对于基于节点的容器（ `boost::unordered++_[++multi++]++set` 、 `boost::unordered++_[++multi++]++map` 、 `boost::unordered++_++node++_++set` 、 `boost::unordered++_++node++_++map` ），其指针和引用永远不会失效。但对于 `boost::unordered++_++flat++_++set` 和 `boost::unordered++_++flat++_++map` ，在发生重哈希时指针和引用将会失效：这是因为这些容器将元素直接存储在桶中，当分配新的桶数组时，必须通过移动构造来转移元素。
In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
与为 `vector` 使用 `reserve` 类似，在插入大量元素之前调用 `reserve` 是一个好主意。这样可以避免代价高昂的重哈希操作，并且让你能够存储迭代器，确信它们不会被失效。如果你要向容器 `x` 插入 `n` 个元素，可以先调用：
`reserve(n)` reserves space for at least `n` elements, allocating enough buckets
`reserve(n)` 为至少 `n` 个元素预留空间，分配足够数量的桶，
so as to not exceed the maximum load factor. + Because the maximum load factor is defined as the number of elements divided by the total number of available buckets, this function is logically equivalent to: + ``` x.rehash(std::ceil(n / x.max_load_factor())) ``` + See the xref:reference/unordered_map.adoc#unordered_map_rehash[reference for more details] on the `rehash` function.
以确保不超过最大负载因子。由于最大负载因子定义为元素数量除以可用桶的总数，该函数在逻辑上等价于：
```cppx.rehash(std::ceil(n / x.max_load_factor()))```
有关 `rehash` 函数的更多详细信息，请参阅 xref:reference/unordered_map.adoc#unordered_map_rehash[参考文档]。
Comparison with Associative Containers
与关联容器的对比
Parameterized by an ordering relation `Compare`
通过排序关系 `Compare` 进行 参数化
Parameterized by a function object `Hash` and an equivalence relation `Pred`
由函数对象`哈希对象`和等价关系`谓词对象`参数化。
O(log(`size()`) + _N_)
O(log(`size()`) + _N_)
Find
查找
Count
计数
`equal_range(k)`
`equal_range(k)`
`lower_bound`,`upper_bound`
`lower_bound`,`upper_bound`
n/a
n/a
`equal_range(k)` returns a range at the end of the container if `k` isn't present in the container. It can't return a positioned range as `k` could be inserted into multiple place. +
equal_range(k) 若键k不存在于容器中，则返回容器末尾的区间。该函数无法返回定位区间，因为k可被插入到多个位置。
It is not specified how member functions other than `rehash` and `reserve` affect the bucket count, although `insert` can only invalidate iterators when the insertion causes the container's load to be greater than the maximum allowed. For most implementations this means that `insert` will only change the number of buckets when this happens. Iterators can be invalidated by calls to `insert`, `rehash` and `reserve`.
标准未明确规定除 `rehash` 和 `reserve` 之外的成员函数如何影响桶数量，但 `insert` 操作仅当导致容器负载超过最大允许值时才会使迭代器失效。在大多数实现中，这意味着 `insert` 仅在此种情况下才会改变桶的数量。迭代器可能因调用 `insert` 、 `rehash` 或 `reserve` 而失效。
``` x.reserve(n); ```
``` x.reserve(n); ```

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In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:与为 `vector` 使用 `reserve` 类似，在插入大量元素之前调用 `reserve` 是一个好主意。这样可以避免代价高昂的重哈希操作，并且让你能够存储迭代器，确信它们不会被失效。如果你要向容器 `x` 插入 `n` 个元素，可以先调用：
06/05/2026
User avatar admin

String added in the repository
In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
In a similar manner to using `reserve` for ``vector``s, it can be a good idea to call `reserve` before inserting a large number of elements. This will get the expensive rehashing out of the way and let you store iterators, safe in the knowledge that they won't be invalidated. If you are inserting `n` elements into container `x`, you could first call:
06/05/2026
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Unit identifier
49690
Source string location
:70
String age
06/05/2026
Last updated
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Source string age
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doc/modules/ROOT/pages/regular_zh_Hans.adoc, string 11