std::unorde...ltimap::find(3)

💖 std::unordered_multimap::find 💖

okay so bestie, this whole page is for std::unorde...ltimap::find(3) from the C++ Standard Libary manual — yes, the header title is literally truncated like that, no cap. We’re talking about std::unordered_multimap::find, and it’s here to help you find an element by key. periodt. ✨

🌸 NAME 🌸

std::unordered_multimap::find — that’s the name, that’s the whole assignment, and honestly? Iconic. 💅

✨ Synopsis ✨

iterator find( const Key& key );             (1) (since C++11)
const_iterator find( const Key& key ) const; (2) (since C++11)
template< class K >                          (3) (since C++20)
iterator find( const K& x );
template< class K >                          (4) (since C++20)
const_iterator find( const K& x ) const;

So here’s the overload tea, bestie:

• (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. This is since C++11.
• (3), (4) — finds an element with key that compares equivalent to the value x. This overload participates in overload resolution only if Hash::is_transparent and KeyEqual::is_transparent are valid and each denotes a type. This assumes that such Hash is callable with both K and Key type, and that the KeyEqual is transparent, which, together, allows calling this function without constructing an instance of Key. This is since C++20.

🎀 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. iykyk 👑

💅 Complexity 💅

Constant on average, worst case linear in the size of the container. Not me memorizing that for the vibe check 😭

🌈 Notes 🌈

Feature-test macro moment, bestie:

• __cpp_lib_generic_unordered_lookup — Value 201811L, Std (C++20), Feature: “Heterogeneous comparison lookup in unordered associative containers; overloads (3,4)”.

🍓 Example 🍓

The example literally starts with // Run this code, so run it, bestie:

        #include <iostream>
        #include <unordered_map>

        int main()
        {
            // Simple comparison demo.
            std::unordered_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";
        }

Output:

Found 2 b

👑 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).

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okay that’s the whole page, bestie 🫶 source: http://cppreference.com; version/date: 2024.06.10; and the footer title is std::unorde...ltimap::find(3). Slay this lookup responsibly. 💖✨