Usage of STL map

map It's mapping , You can map any primitive type to any other primitive type .

map Several characteristics of , The key value inside is unique , If there is a repetition, the previous one will be overwritten .

And if you traverse the access , The container will automatically sort from small to large .

Catalog

1.map Definition

2.map Access to elements within a container

3.map Analysis of commonly used functions

4. Yan Shen

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1.map Definition

map<typename 1, typename 2> mp;

Building in front key, Value after value.

2.map Access to elements within a container

(1). By subscript , take key As a subscript .

(2). By iterator map<typename 1, typename 2>::iterator it;

So you can get the iterator it.

And then use it->first Access key ,it->second Access value .

3.map Analysis of commonly used functions

(1) find(key), The direct return key value is key The iterator of the map of If we can't find a way back end().

(2) erase()

It can be an iterator , It can also be a key , It can also be an interval .

(3) size() The return is map The logarithm of the mapping .

(4) clear() Empty map All elements in

(5) count(), You can count the number of times a key value appears , So it can be used to determine whether there is a key .

4. Yan Shen

It can be used unordered_map To replace map, Replace with a hash map Internal red black tree implementation , But at the expense of sorting , Faster than map faster .

C++ map Container and multimap Containers （STL map Containers ）_MagnumLu The blog of -CSDN Blog _c++ multimap Catalog 1. Associate containers and map Container Overview 2. map Containers 2.1 map Create and initialize the list 2.2 map Common properties of containers （ Method ）2.3 insert data 2.4 Data access and traversal 2.5 Deletion of data 2.6 map Sort keywords in 3. multimap Containers 3.1 Access elements 3.2 Remove elements 1. Associate containers and map Container Overview map A container is one of the associated containers . In the associated container , Bit of object ...https://blog.csdn.net/qq_28584889/article/details/83855734?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165552221116782184663405%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=165552221116782184663405&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~top_positive~default-1-83855734-null-null.142^v17^control,157^v15^new_3&utm_term=multimap&spm=1018.2226.3001.4187