C++ å‚考手册
- C++11
- C++14
- C++17
- C++20
- C++ 编译器支æŒæƒ…况表
- 独立与宿主实现
- C++ è¯è¨€
- C++ 关键è¯
- 预处ç†å™¨
- C++ æ ‡å‡†åº“å¤´æ–‡ä»¶
- å…·åè¦æ±‚
- 功能特性测试 (C++20)
- 工具库
- 类型支æŒï¼ˆåŸºæœ¬ç±»åž‹ã€RTTIã€ç±»åž‹ç‰¹æ€§ï¼‰
- 概念库 (C++20)
- 错误处ç†
- 动æ€å†…å˜ç®¡ç†
- 日期和时间工具
- å—符串库
- 容器库
- std::array
- std::vector
- std::map
- std::unordered_map
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::operator[]
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::get_allocator
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::begin, std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::cbegin
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::empty
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::end, std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::cend
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::unordered_map
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::~unordered_map
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::operator=
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::size
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::max_size
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::clear
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::insert
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::insert_or_assign
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::emplace
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::emplace_hint
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::try_emplace
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::erase
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::swap
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::extract
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::at
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::count
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::find
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::contains
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::equal_range
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::begin(size_type), std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::cbegin(size_type)
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::end(size_type), std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::cend(size_type)
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::bucket_count
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::max_bucket_count
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::bucket_size
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::bucket
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::load_factor
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::max_load_factor
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::rehash
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::reserve
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::hash_function
- std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::key_eq
- operator==,!=(std::unordered_map)
- std::swap(std::unordered_map)
- std::erase_if (std::unordered_map)
- std::unordered_map 的推导指引
- std::priority_queue
- std::span
- std::forward_list
- std::deque
- std::list
- std::set
- std::multiset
- std::multimap
- std::unordered_set
- std::unordered_multiset
- std::unordered_multimap
- std::stack
- std::queue
- std::vector<bool>
- 结点把柄 (C++17)
- 注释
- è¿ä»£å™¨åº“
- 范围库 (C++20)
- 算法库
- 数值库
- 输入/输出库
- 文件系统库
- 本地化库
- æ£åˆ™è¡¨è¾¾å¼åº“
- 原åæ“作库
- 线程支æŒåº“
- 实验性 C++ 特性
- 有用的资æº
- 索引
- std 符å·ç´¢å¼•
- åç¨‹æ”¯æŒ (C++20)
- C++ 关键è¯
ä½ç½®ï¼šé¦–页 > C++ å‚考手册 >容器库 >std::unordered_map > std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::extract
std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::extract
| node_type extract( const_iterator position ); |
(1) | (C++17 èµ·) |
| node_type extract( const key_type& x ); |
(2) | (C++17 èµ·) |
2) è‹¥å®¹å™¨æ‹¥æœ‰å…ƒç´ è€Œå…¶å…³é”®ç‰äºŽ
x ï¼Œåˆ™ä»Žå®¹å™¨è§£é“¾è¯¥å…ƒç´ å¹¶è¿”å›žå 有它的结点把柄。å¦åˆ™ï¼Œè¿”回空结点把柄。任何情况下，å‡ä¸å¤åˆ¶æˆ–ç§»åŠ¨å…ƒç´ ï¼Œåªé‡æŒ‡å‘容器结点的内部指针。
释出结点åªä¼šéžæ³•åŒ–指å‘è¢«é‡Šå‡ºå…ƒç´ çš„è¿ä»£å™¨ï¼Œå¹¶ä¿æŒæœªè¢«æ“¦é™¤å…ƒç´ 的相对顺åºã€‚指å‘è¢«é‡Šå‡ºå…ƒç´ çš„æŒ‡é’ˆå’Œå¼•ç”¨ä¿æŒåˆæ³•ï¼Œä½†åœ¨ç»“点把柄å æœ‰è¯¥å…ƒç´ æ—¶ä¸èƒ½ä½¿ç”¨ï¼šè‹¥å…ƒç´ 被æ’入容器，就能使用它们。
å‚æ•°
| position | - | 指å‘æ¤å®¹å™¨ä¸çš„åˆæ³•è¿ä»£å™¨ |
| x | - | 鉴别è¦è¢«é‡Šå‡ºçš„结点的关键 |
返回值
å æœ‰è¢«é‡Šå‡ºå…ƒç´ çš„ç»“ç‚¹æŠŠæŸ„ï¼Œæˆ–åœ¨é‡è½½ (2) ä¸æ‰¾ä¸åˆ°å…ƒç´ 的情况下为空结点把柄。
å¤æ‚度
1,2) å¹³å‡æƒ…况 O(1) ，最å情况 O(a.size()) 。
注æ„
extract æ˜¯æ›´æ¢ map 的关键而ä¸é‡åˆ†é…的唯一方å¼ï¼š
map<int, string> m{{1, "mango"}, {2, "papaya"}, {3, "guava"}}; auto nh = m.extract(2); nh.key() = 4; m.insert(move(nh)); // m == {{1, "mango"}, {3, "guava"}, {4, "papaya"}}
示例
| æœ¬èŠ‚æœªå®Œæˆ åŽŸå› ï¼šæš‚æ— ç¤ºä¾‹ |
å‚阅
| (C++17) |
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| æ’å…¥å…ƒç´ æˆ–ç»“ç‚¹ (C++17 èµ·) (公开æˆå‘˜å‡½æ•°) | |
| æ“¦é™¤å…ƒç´ (公开æˆå‘˜å‡½æ•°) |