std::unorde...ltiset::swap(3)

💅 std::unorde...ltiset::swap(3) 💅

okay so bestie, you're reading the std::unorde...ltiset::swap(3) page from the C++ Standard Libary — yes, that typo is literally in the header, iconic 😭. This is the whole vibe of swapping two unordered_multisets without touching individual elements. Let's get into it 🫶.

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✨ NAME ✨

• std::unordered_multiset::swap — std::unordered_multiset::swap 💖

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🌸 Synopsis 🌸

void swap( unordered_multiset& other );

(since C++11) (until C++17)

void swap( unordered_multiset& other ) noexcept(/* see below */);

(since C++17)

Exchanges the contents of the container with those of other. Does not invoke any move, copy, or swap operations on individual elements. No cap, it's just a whole-container swap 💅.

All iterators and references remain valid. The end() iterator is invalidated. That's the tea 🫖.

The Hash and KeyEqual objects must be Swappable, and they are exchanged using unqualified calls to non-member swap.

If std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap. Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined). (since C++11)

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🎀 Parameters 🎀

• other — container to exchange the contents with

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🦋 Return value 🦋

(none) — literally nothing comes back, it's giving void energy ✨

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💀 Exceptions 💀

Any exception thrown by the swap of the Hash or KeyEqual objects. (until C++17)

noexcept specification:

noexcept(std::allocator_traits<Allocator>::is_always_equal::value
&& std::is_nothrow_swappable<Hash>::value
&& std::is_nothrow_swappable<key_equal>::value)

(since C++17)

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⭐ Complexity ⭐

Constant.

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🍓 Example 🍓

// Run this code

#include <iostream>
#include <unordered_set>

template<class Os, class Co> Os& operator<<(Os& os, const Co& co)
{
    os << '{';
    for (auto const& i : co)
        os << ' ' << i;
    return os << " } ";
}

int main()
{
    std::unordered_multiset<int> a1{3, 1, 3, 2}, a2{5, 4, 5};

    auto it1 = std::next(a1.begin());
    auto it2 = std::next(a2.begin());

    const int& ref1 = *(a1.begin());
    const int& ref2 = *(a2.begin());

    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' '
              << ref2 << '\n';
    a1.swap(a2);
    std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' '
              << ref2 << '\n';

    // Note that every iterator referring to an element in one
    // container before the swap
    // refers to the same element in the other container after the
    // swap. Same is true
    // for references.
}

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🌈 Possible output: 🌈

{ 2 3 3 1 } { 4 5 5 } 3 5 2 4
{ 4 5 5 } { 2 3 3 1 } 3 5 2 4

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👑 See also 👑

• std::swap(std::unordered_multiset) — specializes the std::swap algorithm (C++11) (function template)

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🧚 Category: 🧚

• conditionally noexcept

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k byeee 💖 this iconic page came from http://cppreference.com, version/date 2024.06.10, and the header std::unorde...ltiset::swap(3) — mwah, go swap your multisets bestie 🫶✨