std::map::find

 

C++

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std::map

Member functions

map::map

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Element access

map::at

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Iterators

map::begin map::cbegin (C++11)

map::end map::cend (C++11)

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Modifiers

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Lookup

map::count

map::find

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map::upper_bound

Observers

map::key_comp

map::value_comp

 

iterator find( const Key& key );
const_iterator find( const Key& key ) const;

Finds an element with key key.

Parameters

key

-

key value of the element to search for

Return value

Iterator to an element with key key. If no such element is found, past-the-end (see end()) iterator is returned.

Complexity

Logarithmic in the size of the container.

See also

count	returns the number of elements matching specific key (public member function)
equal_range	returns range of elements matching a specific key (public member function)

Example

Demonstrates the risk of accessing non-existing elements via operator [].

#include <string>
#include <iostream>
#include <map>
 
int main()
{
    typedef std::map<std::string,int>  mapT;
 
    mapT my_map;
    my_map["first"]=  11;
    my_map["second"]= 23;
 
    mapT::iterator  it= my_map.find("first");
    if( it != my_map.end() ) std::cout << "A: " << it->second << "\n";
 
    it= my_map.find("third");
    if( it != my_map.end() ) std::cout << "B: " << it->second << "\n";
 
    // Accessing a non-existing element creates it
    if( my_map["third"] == 42 ) std::cout << "Oha!\n";
 
    it= my_map.find("third");
    if( it != my_map.end() ) std::cout << "C: " << it->second << "\n";
 
    return 0;
}

Output:

A: 11
C: 0