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Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
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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。
Member function `lower_bound(k)` and `upper_bound(k)`
成员函数`lower_bound(k)`和`upper_bound(k)`
No equivalent. Since the elements aren't ordered `lower_bound` and `upper_bound` would be meaningless.
无对应接口。由于元素无序，`lower_bound `和 `upper_bound `无实际意义。
`equal_range(k)` returns an empty range at the position that `k` would be inserted if `k` isn't present in the container.
若键k不存在于容器中，equal_range(k)会在k 应插入的位置返回一个空区间。
`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。
**Closed-addressing containers:** To find out the bucket that `k` would be inserted into use `bucket(k)`. But remember that an insert can cause the container to rehash - meaning that the element can be inserted into a different bucket.
闭散列容器：使用 bucket (k) 可确定键 k 待插入的哈希桶。需注意，插入操作可能触发容器重新哈希，元素最终会被存入其他哈希桶。
`iterator`, `const_iterator` are of the bidirectional category.
`迭代器`、`常迭代器`的迭代类别为双向迭代器。
`iterator`, `const_iterator` are of at least the forward category.
`迭代器`、`常迭代器`的迭代类别至少为前向迭代器。
Iterators, pointers and references to the container's elements are never invalidated.
指向容器元素的迭代器、指针和引用永远不会失效。
xref:regular.adoc#regular_iterator_invalidation[Iterators can be invalidated by calls to insert or rehash]. +
xref:regular.adoc#regular_iterator_invalidation [调用 insert 或 rehash 可能会导致迭代器失效]。
**Node-based containers:** Pointers and references to the container's elements are never invalidated. + **Flat containers:** Pointers and references to the container's elements are invalidated when rehashing occurs.
基于节点的容器：指向容器元素的指针和引用永远不会失效。
扁平容器：发生重新哈希时，指向容器元素的指针和引用将会失效。
Iterators iterate through the container in the order defined by the comparison object.
迭代器按照比较对象定义的顺序遍历容器。
Iterators iterate through the container in an arbitrary order, that can change as elements are inserted, although equivalent elements are always adjacent.
迭代器以任意顺序遍历容器，该顺序会随元素插入发生变化，但等价元素始终保持相邻。
No equivalent
无对应接口
English Chinese (Simplified Han script) Actions
[#regular] = Regular Containers
[#regular] = 常规容器
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。
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。
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。
No equivalent. Since the elements aren't ordered `lower_bound` and `upper_bound` would be meaningless.
无对应接口。由于元素无序，`lower_bound `和 `upper_bound `无实际意义。
`equal_range(k)` returns an empty range at the position that `k` would be inserted if `k` isn't present in the container.
若键k不存在于容器中，equal_range(k)会在k 应插入的位置返回一个空区间。
**Closed-addressing containers:** To find out the bucket that `k` would be inserted into use `bucket(k)`. But remember that an insert can cause the container to rehash - meaning that the element can be inserted into a different bucket.
闭散列容器：使用 bucket (k) 可确定键 k 待插入的哈希桶。需注意，插入操作可能触发容器重新哈希，元素最终会被存入其他哈希桶。
`iterator`, `const_iterator` are of the bidirectional category.
`迭代器`、`常迭代器`的迭代类别为双向迭代器。
`iterator`, `const_iterator` are of at least the forward category.
`迭代器`、`常迭代器`的迭代类别至少为前向迭代器。
Iterators, pointers and references to the container's elements are never invalidated.
指向容器元素的迭代器、指针和引用永远不会失效。
xref:regular.adoc#regular_iterator_invalidation[Iterators can be invalidated by calls to insert or rehash]. +
xref:regular.adoc#regular_iterator_invalidation [调用 insert 或 rehash 可能会导致迭代器失效]。
**Node-based containers:** Pointers and references to the container's elements are never invalidated. + **Flat containers:** Pointers and references to the container's elements are invalidated when rehashing occurs.
基于节点的容器：指向容器元素的指针和引用永远不会失效。
扁平容器：发生重新哈希时，指向容器元素的指针和引用将会失效。
Iterators iterate through the container in the order defined by the comparison object.
迭代器按照比较对象定义的顺序遍历容器。
When inserting with a hint, implementations are permitted to ignore the hint.
使用提示迭代器插入元素时，实现允许忽略该提示。
---
---
Construction of empty container
空容器的构造
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。

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Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
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。
06/05/2026
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Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
06/05/2026
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safe-html, strict-same
Unit identifier
49703
Source string location
:100
String age
06/05/2026
Last updated
06/06/2026
Source string age
06/05/2026
Translation file AsciiDoc file
doc/modules/ROOT/pages/regular_zh_Hans.adoc, string 24