From cppreference.com
iteratorfind(constKey&key); (1) (since C++23)const_iteratorfind(constKey&key)const; (2) (since C++23)template<classK>iteratorfind(constK&x); (3)(since C++23)template<classK>const_iteratorfind(constK&x)const; (4)(since C++23)1,2) Finds an element with key equivalent to key.
3,4) Finds an element with key that compares equivalent to the value x. This overload participates in overload resolution only if the qualified-id Compare::is_transparent is valid and denotes a type. It allows calling this function without constructing an instance of Key.
Parameters
key - key value of the element to search for x - a value of any type that can be transparently compared with a key Return value
An iterator to the requested element. If no such element is found, past-the-end (see end()) iterator is returned.
Complexity
Logarithmic in the size of the container.
Example
Run this code
#include<iostream>#include<flat_map>structLightKey{intx;};structFatKey{intx;intdata[1000];// a heavy blob};// As detailed above, the container must use std::less<> (or other transparent// Comparator) to access these overloads. This includes standard overloads,// such as comparison between std::string and std::string_view.booloperator<(constFatKey&fk,constLightKey&lk){returnfk.x<lk.x;}booloperator<(constLightKey&lk,constFatKey&fk){returnlk.x<fk.x;}booloperator<(constFatKey&fk1,constFatKey&fk2){returnfk1.x<fk2.x;}intmain(){// Simple comparison demo.std::flat_map<int,char>example{{1,'a'},{2,'b'}};if(autosearch=example.find(2);search!=example.end())std::cout<<"Found "<<search->first<<' '<<search->second<<'\n';elsestd::cout<<"Not found\n";// Transparent comparison demo.std::flat_map<FatKey,char,std::less<>>example2{{{1,{}},'a'},{{2,{}},'b'}};LightKeylk={2};if(autosearch=example2.find(lk);search!=example2.end())std::cout<<"Found "<<search->first.x<<' '<<search->second<<'\n';elsestd::cout<<"Not found\n";// Obtaining const iterators.// Compiler decides whether to return iterator of (non) const type by way of// accessing map; to prevent intentional modification, one of the simplest// options is to access the map via a constant reference.constauto&example2ref=example2;if(autosearch=example2ref.find(lk);search!=example2.end()){std::cout<<"Found "<<search->first.x<<' '<<search->second<<'\n';// search->second = 'c'; // error: assignment of member// 'std::pair<const FatKey, char>::second'// in read-only object}}Output:
Found 2 b Found 2 b Found 2 b See also
access specified element with bounds checking
(public member function)
access or insert specified element
(public member function)
returns the number of elements matching specific key
(public member function)
returns range of elements matching a specific key
(public member function)