First time to know STL

STL brief introduction ：

STL（Standard Template Library）, Standard template library , It's an industrial strength , efficient C++ library . Is a set of powerful C++ Template class , Provides generic template classes and functions , These template classes and functions can implement a variety of popular and commonly used algorithms and data structures , Like a vector 、 Linked list 、 queue 、 Stack .

​C++ The core of the standard template library includes containers (Containers）、 Algorithm （Algorithms）、 iterator （iterators） Three components , among 1. A container is a collection of objects of a certain type ,C++ There are different types of containers , such as deque、list、vector、map etc. ;2. The algorithm works on the container . They provide ways to perform various operations , Includes initializing the contents of the container 、 Sort 、 Search and conversion operations ;3. Iterators are used to traverse the elements of an object collection . These collections can be containers , It could also be a subset of the container . All three components come with rich predefined functions , Help us deal with complex tasks in a simple way .

STL Characteristics ：

STL One of the most important features of is the separation of data structure and algorithm ：

​ Although it's a simple concept , But this separation does make STL Become very versatile . for example , because STL Of sort() Functions are completely generic , You can use it to manipulate almost any set of data , Including the list , Containers and arrays ;

STL Another important feature is that it is not object-oriented ：

​ In order to be universal enough ,STL Mainly depends on templates rather than encapsulation , Inheritance and polymorphism ——OOP The three elements of . you are here STL You can't find any obvious class inheritance relationships in . It's like a kind of retrogression , But this is what makes STL The components have the underlying characteristics of wide commonality . in addition , because STL It's based on templates , The use of inline functions makes the generated code short and efficient ;

STL Components ：

​ STL Components It mainly includes Containers , iterator 、 Algorithms and affine functions .

Containers

Containers are used to store and manage a collection of objects of a certain kind .

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​ For example, a fish tank is a container for goldfish . Every container has its advantages and disadvantages . To meet the needs of the program ,STL A variety of container types are available , The container can be arrays or linked lists, Or each element has a special key value .

iterator

Iterators are used to traverse elements of an object cluster . Object clusters can be containers , It could be part of the container .

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​ The main purpose of iterators is to provide a small set of common interfaces for containers . Use this interface , An operation can progress to the next element in the cluster . Each container provides its own iterator . The iterator understands the internal structure of the container , So it's going to go right . The interface of an iterator is similar to a general pointer .

Algorithm

Used to handle elements in the cluster , You can search for... For different purposes 、 Sort 、 modify 、 Use those elements .

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​ All container iterators provide a consistent interface , With the help of iterators , Algorithmic programs can be used in any container .

STL One of the features of is the separation of data and operations . Data is managed by container categories , Operations are defined by customizable algorithms . An iterator acts in between “ adhesive ”, So that the algorithm can interact with the container .

STL Another feature of is that components can operate against any type .“ Standard template library ” The name means “ Any type is acceptable ” The template of , And these types can perform the necessary operations .

stay STL in , Containers are divided into Sequential containers and Associative containers Two categories: , The function of iterator is to traverse all or part of the objects in the container . Iterators can be divided into 5 Species and genera , this 5 The species belong to two types ： Bidirectional iterators and random access iterators .

SIL The algorithms provided in include searching for 、 Sort 、 Copy 、 reorder 、 modify 、 Numerical operation, etc .

functor

STL Imitation functions are widely used in . Imitation function has the powerful power of generic programming , Is an example of a purely abstract concept .

STL Containers and algorithms ：

Containers

​ STL Contains many container classes . A container class is a class that can contain other objects , Like arrays and queue stacks, data structures contain integers 、 decimal 、 Class and other data members .STL Can contain common vector classes 、 List class 、 Two way queue class 、 Collection classes 、 Graph class, etc , Each class is a template , These templates can contain various types of objects .

The following code is commonly used vector Assignment method ：

vector <int> l;
for (int i =0;i <100;i++ )
l.push_back (i);

The following code uses map The container manages two-dimensional elements ：

map <string, string, less <string>> cap; // Sort from small to large 
cap ["Ark"] ="Little Rock";
cap ["New"] ="Albany";

map Be similar to Two dimensional array , But it's much more flexible than a two-dimensional array .

at present ,STL The containers already provided in are mainly as follows ：

• vector ： A vector .
• list ： A two-way linked list container , Completed the standard C++ All functions of linked list in data structure .
• queue ： A queue container , Completed the standard C++ All the functions of the queue in the data structure .
• stack ： A stack container , Completed the standard C++ All functions of the stack in the data structure .
• deque ： Double ended queue container , Completed the standard C++ All functions of the stack in the data structure .
• priority_queue ： A queue container sorted by value .
• set ： A collection container .
• multiset ： A collection container that allows duplicate elements to occur .
• map <key, val>： An associative array container .
• multimap <key, val>： One that allows repetition key Value's associative array container .

The above container design is efficient , The interface is also provided . Programmers can use them wherever appropriate .

Containers Can be divided into Sequential containers and Associative containers Two categories: . Sequential containers There are mainly vector、list and deque; Associative containers Include set、map、multiset and multimap Container template class .

Algorithm

STL Provides a lot of data structure algorithms . These algorithms are in the namespace std Within the scope of , By including header files <algorithm> To get the right to use .

Some common algorithms are as follows ：

• for_each();
• find();
• find_if();
• count();
• count_if();
• replace();
• replace_if();
• copy();
• unique_copy();
• sort();
• equal_range();
• merge();

STL All algorithms in are implemented based on templates .

Out of curiosity , From browsing the Internet without permission , No systematic , Overall learning , If there are any inaccuracies and deficiencies, please give advice ψ(｀∇´)ψ（￣︶￣）