C++ 中map 中迭代器的简单使用：

Posted 2020-07-25 the_tops ----

public member function

<map>

std::map::find

      iterator find (const key_type& k);
const_iterator find (const key_type& k) const;

Get iterator to element

Searches the container for an element with a key equivalent to k and returns an iterator to it if found, otherwise it returns an iterator to map::end.

Two keys are considered equivalent if the container‘s comparison object returns false reflexively (i.e., no matter the order in which the elements are passed as arguments).

Another member function, map::count, can be used to just check whether a particular key exists.

Parameters

k

Key to be searched for.
Member type key_type is the type of the keys for the elements in the container, defined in map as an alias of its first template parameter (Key).

 

Return value

An iterator to the element, if an element with specified key is found, or map::end otherwise.

If the map object is const-qualified, the function returns a const_iterator. Otherwise, it returns an iterator.

Member types iterator and const_iterator are bidirectional iterator types pointing to elements (of type value_type).
Notice that value_type in map containers is an alias of pair<const key_type, mapped_type>.

Example

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// map::find #include <iostream> #include <map> int main () { std::map<char,int> mymap; std::map<char,int>::iterator it; mymap[‘a‘]=50; mymap[‘b‘]=100; mymap[‘c‘]=150; mymap[‘d‘]=200; it = mymap.find(‘b‘); if (it != mymap.end()) mymap.erase (it); // print content: std::cout << "elements in mymap:" << ‘\n‘; std::cout << "a => " << mymap.find(‘a‘)->second << ‘\n‘; std::cout << "c => " << mymap.find(‘c‘)->second << ‘\n‘; std::cout << "d => " << mymap.find(‘d‘)->second << ‘\n‘; return 0; }

Edit & Run

Output:

elements in mymap: a => 50 c => 150 d => 200