标准库头文件 <unordered_map>
此头文件是容器库的一部分。
包含 | |
(C++20) |
三路比较运算符支持 |
(C++11) |
std::initializer_list 类模板 |
类 | |
(C++11 起) |
键值对的集合,按照键生成散列,键是唯一的 (类模板) |
(C++11 起) |
键值对的集合,按照键生成散列 (类模板) |
函数 | |
(C++20 中移除) |
比较 unordered_map 中的值 (函数模板) |
特化 std::swap 算法 (函数模板) | |
(C++20) |
擦除所有满足特定判别标准的元素 (函数模板) |
(C++20 中移除) |
比较 unordered_multimap 中的值 (函数模板) |
特化 std::swap 算法 (函数模板) | |
擦除所有满足特定判别标准的元素 (函数模板) | |
范围访问 | |
(C++11)(C++14) |
返回指向容器或数组起始的迭代器 (函数模板) |
(C++11)(C++14) |
返回指向容器或数组结尾的迭代器 (函数模板) |
(C++14) |
返回指向一个容器或数组的逆向迭代器 (函数模板) |
(C++14) |
返回容器或数组的逆向尾迭代器 (函数模板) |
(C++17)(C++20) |
返回容器或数组的大小 (函数模板) |
(C++17) |
检查容器是否为空 (函数模板) |
(C++17) |
获得指向底层数组的指针 (函数模板) |
概要
#include <compare> #include <initializer_list> namespace std { // 类模板 unordered_map template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Alloc = allocator<pair<const Key, T>>> class unordered_map; // 类模板 unordered_multimap template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Alloc = allocator<pair<const Key, T>>> class unordered_multimap; template<class Key, class T, class Hash, class Pred, class Alloc> bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a, const unordered_map<Key, T, Hash, Pred, Alloc>& b); template<class Key, class T, class Hash, class Pred, class Alloc> bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a, const unordered_multimap<Key, T, Hash, Pred, Alloc>& b); 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))); template<class Key, class T, class Hash, class Pred, class Alloc> void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x, unordered_multimap<Key, T, Hash, Pred, Alloc>& y) noexcept(noexcept(x.swap(y))); 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); template<class K, class T, class H, class P, class A, class Predicate> typename unordered_multimap<K, T, H, P, A>::size_type erase_if(unordered_multimap<K, T, H, P, A>& c, Predicate pred); namespace pmr { template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>> using unordered_map = std::unordered_map<Key, T, Hash, Pred, polymorphic_allocator<pair<const Key, T>>>; template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>> using unordered_multimap = std::unordered_multimap<Key, T, Hash, Pred, polymorphic_allocator<pair<const Key, T>>>; } }
类模板 std::unordered_map
namespace std { template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>> class unordered_map { public: // 类型 using key_type = Key; using mapped_type = T; using value_type = pair<const Key, T>; using hasher = Hash; using key_equal = Pred; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = /* 由实现定义 */; using difference_type = /* 由实现定义 */; using iterator = /* 由实现定义 */; using const_iterator = /* 由实现定义 */; using local_iterator = /* 由实现定义 */; using const_local_iterator = /* 由实现定义 */; using node_type = /* 未指明 */; using insert_return_type = /*insert-return-type*/<iterator, node_type>; // 构造/复制/销毁 unordered_map(); explicit unordered_map(size_type n, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); template<class InputIt> unordered_map(InputIt f, InputIt l, size_type n = /* 见描述 */, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); unordered_map(const unordered_map&); unordered_map(unordered_map&&); explicit unordered_map(const Allocator&); unordered_map(const unordered_map&, const Allocator&); unordered_map(unordered_map&&, const Allocator&); unordered_map(initializer_list<value_type> il, size_type n = /* 见描述 */, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); unordered_map(size_type n, const allocator_type& a) : unordered_map(n, hasher(), key_equal(), a) { } unordered_map(size_type n, const hasher& hf, const allocator_type& a) : unordered_map(n, hf, key_equal(), a) { } template<class InputIt> unordered_map(InputIt f, InputIt l, size_type n, const allocator_type& a) : unordered_map(f, l, n, hasher(), key_equal(), a) { } template<class InputIt> unordered_map(InputIt f, InputIt l, size_type n, const hasher& hf, const allocator_type& a) : unordered_map(f, l, n, hf, key_equal(), a) { } unordered_map(initializer_list<value_type> il, size_type n, const allocator_type& a) : unordered_map(il, n, hasher(), key_equal(), a) { } unordered_map(initializer_list<value_type> il, size_type n, const hasher& hf, const allocator_type& a) : unordered_map(il, n, hf, key_equal(), a) { } ~unordered_map(); unordered_map& operator=(const unordered_map&); unordered_map& operator=(unordered_map&&) noexcept(allocator_traits<Allocator>::is_always_equal::value && is_nothrow_move_assignable_v<Hash> && is_nothrow_move_assignable_v<Pred>); unordered_map& operator=(initializer_list<value_type>); allocator_type get_allocator() const noexcept; // 迭代器 iterator begin() noexcept; const_iterator begin() const noexcept; iterator end() noexcept; const_iterator end() const noexcept; const_iterator cbegin() const noexcept; const_iterator cend() const noexcept; // 容量 [[nodiscard]] bool empty() const noexcept; size_type size() const noexcept; size_type max_size() const noexcept; // 修改器 template<class... Args> pair<iterator, bool> emplace(Args&&... args); template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args); pair<iterator, bool> insert(const value_type& obj); pair<iterator, bool> insert(value_type&& obj); template<class P> pair<iterator, bool> insert(P&& obj); iterator insert(const_iterator hint, const value_type& obj); iterator insert(const_iterator hint, value_type&& obj); template<class P> iterator insert(const_iterator hint, P&& obj); template<class InputIt> void insert(InputIt first, InputIt last); void insert(initializer_list<value_type>); node_type extract(const_iterator position); node_type extract(const key_type& x); insert_return_type insert(node_type&& nh); iterator insert(const_iterator hint, node_type&& nh); template<class... Args> pair<iterator, bool> try_emplace(const key_type& k, Args&&... args); template<class... Args> pair<iterator, bool> try_emplace(key_type&& k, Args&&... args); template<class... Args> iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args); template<class... Args> iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args); template<class M> pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj); template<class M> pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj); template<class M> iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj); template<class M> iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj); iterator erase(iterator position); iterator erase(const_iterator position); size_type erase(const key_type& k); iterator erase(const_iterator first, const_iterator last); void swap(unordered_map&) noexcept(allocator_traits<Allocator>::is_always_equal::value && is_nothrow_swappable_v<Hash> && is_nothrow_swappable_v<Pred>); void clear() noexcept; template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>&& source); template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source); // 观察器 hasher hash_function() const; key_equal key_eq() const; // map 操作 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<class K> size_type count(const key_type& k) const; template<class K> size_type count(const K& k) const; bool contains(const key_type& k) const; template<class K> bool contains(const K& k) const; pair<iterator, iterator> equal_range(const key_type& k); pair<const_iterator, const_iterator> equal_range(const key_type& k) const; template<class K> pair<iterator, iterator> equal_range(const K& k); template<class K> pair<const_iterator, const_iterator> equal_range(const K& k) const; // 元素访问 mapped_type& operator[](const key_type& k); mapped_type& operator[](key_type&& k); mapped_type& at(const key_type& k); const mapped_type& at(const key_type& k) const; // 桶接口 size_type bucket_count() const noexcept; size_type max_bucket_count() const noexcept; size_type bucket_size(size_type n) const; size_type bucket(const key_type& k) const; local_iterator begin(size_type n); const_local_iterator begin(size_type n) const; local_iterator end(size_type n); const_local_iterator end(size_type n) const; const_local_iterator cbegin(size_type n) const; const_local_iterator cend(size_type n) const; // 散列策略 float load_factor() const noexcept; float max_load_factor() const noexcept; void max_load_factor(float z); void rehash(size_type n); void reserve(size_type n); }; template<class InputIt, class Hash = hash</*iter-key-type*/<InputIt>>, class Pred = equal_to</*iter-key-type*/<InputIt>>, class Allocator = allocator</*iter-to-alloc-type*/<InputIt>>> unordered_map(InputIt, InputIt, typename /* 见描述 */::size_type = /* 见描述 */, Hash = Hash(), Pred = Pred(), Allocator = Allocator()) -> unordered_map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>, Hash, Pred, Allocator>; template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>> unordered_map(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type = /* 见描述 */, Hash = Hash(), Pred = Pred(), Allocator = Allocator()) -> unordered_map<Key, T, Hash, Pred, Allocator>; template<class InputIt, class Allocator> unordered_map(InputIt, InputIt, typename /* 见描述 */::size_type, Allocator) -> unordered_map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>, hash</*iter-key-type*/<InputIt>>, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class InputIt, class Allocator> unordered_map(InputIt, InputIt, Allocator) -> unordered_map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIte>, hash</*iter-key-type*/<InputIt>>, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class InputIt, class Hash, class Allocator> unordered_map(InputIt, InputIt, typename /* 见描述 */::size_type, Hash, Allocator) -> unordered_map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>, Hash, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class Key, class T, class Allocator> unordered_map(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type, Allocator) -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>; template<class Key, class T, class Allocator> unordered_map(initializer_list<pair<Key, T>>, Allocator) -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>; template<class Key, class T, class Hash, class Allocator> unordered_map(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type, Hash, Allocator) -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>; // 交换 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))); }
Class template std::unordered_multimap
namespace std { template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>> class unordered_multimap { public: // 类型 using key_type = Key; using mapped_type = T; using value_type = pair<const Key, T>; using hasher = Hash; using key_equal = Pred; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = /* 由实现定义 */; using difference_type = /* 由实现定义 */; using iterator = /* 由实现定义 */; using const_iterator = /* 由实现定义 */; using local_iterator = /* 由实现定义 */; using const_local_iterator = /* 由实现定义 */; using node_type = /* 未指明 */; // 构造/复制/销毁 unordered_multimap(); explicit unordered_multimap(size_type n, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); template<class InputIt> unordered_multimap(InputIt f, InputIt l, size_type n = /* 见描述 */, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); unordered_multimap(const unordered_multimap&); unordered_multimap(unordered_multimap&&); explicit unordered_multimap(const Allocator&); unordered_multimap(const unordered_multimap&, const Allocator&); unordered_multimap(unordered_multimap&&, const Allocator&); unordered_multimap(initializer_list<value_type> il, size_type n = /* 见描述 */, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); unordered_multimap(size_type n, const allocator_type& a) : unordered_multimap(n, hasher(), key_equal(), a) { } unordered_multimap(size_type n, const hasher& hf, const allocator_type& a) : unordered_multimap(n, hf, key_equal(), a) { } template<class InputIt> unordered_multimap(InputIt f, InputIt l, size_type n, const allocator_type& a) : unordered_multimap(f, l, n, hasher(), key_equal(), a) { } template<class InputIt> unordered_multimap(InputIt f, InputIt l, size_type n, const hasher& hf, const allocator_type& a) : unordered_multimap(f, l, n, hf, key_equal(), a) { } unordered_multimap(initializer_list<value_type> il, size_type n, const allocator_type& a) : unordered_multimap(il, n, hasher(), key_equal(), a) { } unordered_multimap(initializer_list<value_type> il, size_type n, const hasher& hf, const allocator_type& a) : unordered_multimap(il, n, hf, key_equal(), a) { } ~unordered_multimap(); unordered_multimap& operator=(const unordered_multimap&); unordered_multimap& operator=(unordered_multimap&&) noexcept(allocator_traits<Allocator>::is_always_equal::value && is_nothrow_move_assignable_v<Hash> && is_nothrow_move_assignable_v<Pred>); unordered_multimap& operator=(initializer_list<value_type>); allocator_type get_allocator() const noexcept; // 迭代器 iterator begin() noexcept; const_iterator begin() const noexcept; iterator end() noexcept; const_iterator end() const noexcept; const_iterator cbegin() const noexcept; const_iterator cend() const noexcept; // 容量 [[nodiscard]] bool empty() const noexcept; size_type size() const noexcept; size_type max_size() const noexcept; // 修改器 template<class... Args> iterator emplace(Args&&... args); template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args); iterator insert(const value_type& obj); iterator insert(value_type&& obj); template<class P> iterator insert(P&& obj); iterator insert(const_iterator hint, const value_type& obj); iterator insert(const_iterator hint, value_type&& obj); template<class P> iterator insert(const_iterator hint, P&& obj); template<class InputIt> void insert(InputIt first, InputIt last); void insert(initializer_list<value_type>); node_type extract(const_iterator position); node_type extract(const key_type& x); iterator insert(node_type&& nh); iterator insert(const_iterator hint, node_type&& nh); iterator erase(iterator position); iterator erase(const_iterator position); size_type erase(const key_type& k); iterator erase(const_iterator first, const_iterator last); void swap(unordered_multimap&) noexcept(allocator_traits<Allocator>::is_always_equal::value && is_nothrow_swappable_v<Hash> && is_nothrow_swappable_v<Pred>); void clear() noexcept; template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source); template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>&& source); // 观察器 hasher hash_function() const; key_equal key_eq() const; // map 操作 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; size_type count(const key_type& k) const; template<class K> size_type count(const K& k) const; bool contains(const key_type& k) const; template<class K> bool contains(const K& k) const; pair<iterator, iterator> equal_range(const key_type& k); pair<const_iterator, const_iterator> equal_range(const key_type& k) const; template<class K> pair<iterator, iterator> equal_range(const K& k); template<class K> pair<const_iterator, const_iterator> equal_range(const K& k) const; // 桶接口 size_type bucket_count() const noexcept; size_type max_bucket_count() const noexcept; size_type bucket_size(size_type n) const; size_type bucket(const key_type& k) const; local_iterator begin(size_type n); const_local_iterator begin(size_type n) const; local_iterator end(size_type n); const_local_iterator end(size_type n) const; const_local_iterator cbegin(size_type n) const; const_local_iterator cend(size_type n) const; // 散列策略 float load_factor() const noexcept; float max_load_factor() const noexcept; void max_load_factor(float z); void rehash(size_type n); void reserve(size_type n); }; template<class InputIt, class Hash = hash</*iter-key-type*/<InputIt>>, class Pred = equal_to</*iter-key-type*/<InputIt>>, class Allocator = allocator</*iter-to-alloc-type*/<InputIt>>> unordered_multimap(InputIt, InputIt, typename /* 见描述 */::size_type = /* 见描述 */, Hash = Hash(), Pred = Pred(), Allocator = Allocator()) -> unordered_multimap<iter-key-type<InputIt>, iter-mapped-type<InputIt>, Hash, Pred, Allocator>; template<class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>> unordered_multimap(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type = /* 见描述 */, Hash = Hash(), Pred = Pred(), Allocator = Allocator()) -> unordered_multimap<Key, T, Hash, Pred, Allocator>; template<class InputIt, class Allocator> unordered_multimap(InputIt, InputIt, typename /* 见描述 */::size_type, Allocator) -> unordered_multimap</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>, hash</*iter-key-type*/<InputIt>>, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class InputIt, class Allocator> unordered_multimap(InputIt, InputIt, Allocator) -> unordered_multimap</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>, hash</*iter-key-type*/<InputIt>>, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class InputIt, class Hash, class Allocator> unordered_multimap(InputIt, InputIt, typename /* 见描述 */::size_type, Hash, Allocator) -> unordered_multimap</*iter-key-type*/<InputIt>, iter-mapped-type<InputIt>, Hash, equal_to</*iter-key-type*/<InputIt>>, Allocator>; template<class Key, class T, class Allocator> unordered_multimap(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type, Allocator) -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>; template<class Key, class T, class Allocator> unordered_multimap(initializer_list<pair<Key, T>>, Allocator) -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>; template<class Key, class T, class Hash, class Allocator> unordered_multimap(initializer_list<pair<Key, T>>, typename /* 见描述 */::size_type, Hash, Allocator) -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>; // 交换 template<class Key, class T, class Hash, class Pred, class Alloc> void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x, unordered_multimap<Key, T, Hash, Pred, Alloc>& y) noexcept(noexcept(x.swap(y))); }