C++

Reference

<unordered_map>

unordered_map

public member function
<unordered_map>

std::unordered_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 k as key and returns an iterator to it if found, otherwise it returns an iterator to unordered_map::end (the element past the end of the container).

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

The mapped value can also be accessed directly by using member functions at or operator[].

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 unordered_map as an alias of its first template parameter (Key).

Return value

An iterator to the element, if the specified key value is found, or unordered_map::end if the specified key is not found in the container.

Member types iterator and const_iterator are forward iterator types.

Example

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// unordered_map::find
#include <iostream>
#include <string>
#include <unordered_map>

int main ()
{
  std::unordered_map<std::string,double> mymap = {
     {"mom",5.4},
     {"dad",6.1},
     {"bro",5.9} };

  std::string input;
  std::cout << "who? ";
  getline (std::cin,input);

  std::unordered_map<std::string,double>::const_iterator got = mymap.find (input);

  if ( got == mymap.end() )
    std::cout << "not found";
  else
    std::cout << got->first << " is " << got->second;

  std::cout << std::endl;

  return 0;
}

Possible output:
who? dad
dad is 6.1


Complexity

Average case: constant.
Worst case: linear in container size.

Iterator validity

No changes.

See also

unordered_map::count
Count elements with a specific key (public member function)
unordered_map::operator[]
Access element (public member function)
unordered_map::at
Access element (public member function)