std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>:: find
From cppreference.com
<
cpp
|
container
|
flat multimap
|
iterator find
(
const
Key
&
key
)
;
|
(1) | (since C++23) |
|
const_iterator find
(
const
Key
&
key
)
const
;
|
(2) | (since C++23) |
|
template
<
class
K
>
iterator find ( const K & x ) ; |
(3) | (since C++23) |
|
template
<
class
K
>
const_iterator find ( const K & x ) const ; |
(4) | (since C++23) |
1,2)
Finds an element with key equivalent to
key
. If there are several elements with the requested key in the container, any of them may be returned.
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> struct LightKey { int x; }; struct FatKey { int x; int data[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. bool operator<(const FatKey& fk, const LightKey& lk) { return fk.x < lk.x; } bool operator<(const LightKey& lk, const FatKey& fk) { return lk.x < fk.x; } bool operator<(const FatKey& fk1, const FatKey& fk2) { return fk1.x < fk2.x; } int main() { // Simple comparison demo. std::flat_multimap<int, char> example{{1, 'a'}, {2, 'b'}}; if (auto search = example.find(2); search != example.end()) std::cout << "Found " << search->first << ' ' << search->second << '\n'; else std::cout << "Not found\n"; // Transparent comparison demo. std::flat_multimap<FatKey, char, std::less<>> example2{{{1, {}}, 'a'}, {{2, {}}, 'b'}}; LightKey lk = {2}; if (auto search = example2.find(lk); search != example2.end()) std::cout << "Found " << search->first.x << ' ' << search->second << '\n'; else std::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. const auto& example2ref = example2; if (auto search = 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
|
returns the number of elements matching specific key
(public member function) |
|
|
returns range of elements matching a specific key
(public member function) |