container,algorith,iterate

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http://morningspace.51.net/resource/stlintro/stlintro.html

 

標準容器

C++標準容器分爲序列容器和關聯容器，對於序列容器，C++提供的基本序列有

vector 支持隨機訪問,不適合作插入和刪除操做頻繁的場景

list 雙向鏈表，適合作元素的插入和刪除，不是隨機訪問

deque 也是一個雙端序列，可是通過優化，其雙端操做效率相似list,隨即訪問效率接近vector。

從它們出發，經過定義適當的藉口，生成了

stack 默認用deque實現

queue 默認是deque實現

priority_queue 默認是vector保存元素，實現最多是heap

對於關聯容器，C++提供的有:

map 映射

mulitimap 多重映射，相比map，容許重複的key

set 被看作是一個map，其中的值是可有可無的

mulitiset 相比set,容許重複的key

bitset 位集合

hash_map 散列映射,經過實現一個散列函數，將容器實現爲一個散列表，以減小查找元素所須要的時間

 

標準容器具體用法能夠參考C++在線手冊STL容器:http://www.cplusplus.com/reference/stl/

 

 

Standard library[edit]

The C++ standard consists of two parts: the core language and the C++ Standard Library. C++ programmers expect the latter on every major implementation of C++; it includes vectors, lists, maps, algorithms (find, for_each, binary_search, random_shuffle, etc.), sets, queues, stacks, arrays, tuples, input/output facilities (iostream, for reading from and writing to the console and files), smart pointers for automatic memory management, regular expression support, multi-threading library, atomics support (allowing a variable to be read or written to by at most one thread at a time without any external synchronisation), time utilities (measurement, getting current time, etc.), a system for converting error reporting that doesn't use C++ exceptions into C++ exceptions, a random number generator and a slightly modified version of the C standard library (to make it comply with the C++ type system).

A large part of the C++ library is based on the Standard Template Library (STL). Useful tools provided by the STL include containers as the collections of objects (such as vectors and lists), iterators that provide array-like access to containers, and algorithms that perform operations such as searching and sorting.

Furthermore, (multi)maps (associative arrays) and (multi)sets are provided, all of which export compatible interfaces. Therefore, using templates it is possible to write generic algorithms that work with any container or on any sequence defined by iterators. As in C, the features of the libraryare accessed by using the #include directive to include a standard header. C++ provides 105 standard headers, of which 27 are deprecated.

The standard incorporates the STL that was originally designed by Alexander Stepanov, who experimented with generic algorithms and containers for many years. When he started with C++, he finally found a language where it was possible to create generic algorithms (e.g., STL sort) that perform even better than, for example, the C standard library qsort, thanks to C++ features like using inlining and compile-time binding instead of function pointers. The standard does not refer to it as "STL", as it is merely a part of the standard library, but the term is still widely used to distinguish it from the rest of the standard library (input/output streams, internationalization, diagnostics, the C library subset, etc.).^[50]

Most C++ compilers, and all major ones, provide a standards conforming implementation of the C++ standard library.

算法和函數對象

容器自己之因此有用，是由於容器提供了一些基本操做，如肯定大小,迭代，複製，排序，查找等。標準庫提供了許多算法，服務於容器用戶的最廣泛和最基本的須要。

標準庫算法不過就是60個，每一個算法都描述爲一個模板函數或一組模板函數,例如最經常使用的排序算法:sort,能以很好的平均效率排序，建議排序都用sort替換C語言的qsort，sort能夠更好結合容器。

標準庫算法和函數對象的教程能夠參考C++之父的C++程序設計語言的算法和函數對象,這一章內容能夠教你如何使用標準庫算法和函數對象。

標準庫算法的聲明在<algorithm>,函數對象在<functional>裏。

 

標準庫算法具體用法參考C++在線手冊STL算法:http://www.cplusplus.com/reference/algorithm/

 

迭代器和分配器

迭代器是鏈接容器和算法的紐帶，讓寫算法的人沒必要關心各類數據結構的具體細節，而分配器提供了一個映射，將低級的字節形式的數據模型映射到高級的對象模型。

迭代器是每一個程序員都須要關心的概念之一，可是分配器僅僅是一個支持機制，標準庫已經提供了默認的分配器，不多有程序員須要去寫新的分配器。

迭代器在接觸STL容器就會了解了，通常迭代器分爲正向迭代器，反向迭代器，插入迭代器，帶檢查的迭代器。

至於分配器提供了一套分配和釋放存儲的標準方式，標準庫提供了一個標準分配器，在<memory>裏的標準allocator模板用operator new()分配存儲，全部的標準容器在默認狀況下使用它，固然你也能夠本身實現一個分配器，容器的實現須要一次次的allocate()或者deallocate()對象，意味着new的大量調用，你能夠採用一個固定大小存儲塊的存儲池，能夠比常規的更通用的operator new()的效率高一些。