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std::set::swap(3) C++ Standard Libary std::set::swap(3) NAME std::set::swap - std::set::swap Synopsis void swap( set& other ); (until C++17) void swap( set& 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. All iterators and references remain valid. The past-the-end iterator is invalidated. The Compare objects must be Swappable, and they are exchanged using unqualified call to non-member swap. If std::allocator_traits<allocator_type>::propagate_on_con- tainer_swap::value is true, then the allocators are exchanged using an unqualified call to (since non-member swap. Otherwise, they are not swapped (and if get_alloca- tor() != C++11) other.get_allocator(), the behavior is undefined). Parameters other - container to exchange the contents with Return value (none) Exceptions Any exception thrown by the swap of the Compare objects. (until C++17) noexcept specification: noexcept(std::allocator_traits<Allocator>::is_always_equal::value (since C++17) && std::is_nothrow_swappable<Compare>::value) Complexity Constant. Example // Run this code #include <functional> #include <iostream> #include <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::set<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 con- tainer before the swap // refers to the same element in the other container after the swap. Same is true // for references. struct Cmp : std::less<int> { int id{}; Cmp(int i) : id{i} { } }; std::set<int, Cmp> s1{ {2, 2, 1, 1}, Cmp{6} }, s2{ {4, 4, 3, 3}, Cmp{9} }; std::cout << s1 << s2 << s1.key_comp().id << ' ' << s2.key_comp().id << '\n'; s1.swap(s2); std::cout << s1 << s2 << s1.key_comp().id << ' ' << s2.key_comp().id << '\n'; // So, comparator objects (Cmp) are also exchanged after the swap. } Output: { 1 2 3 } { 4 5 } 2 5 1 4 { 4 5 } { 1 2 3 } 2 5 1 4 { 1 2 } { 3 4 } 6 9 { 3 4 } { 1 2 } 9 6 See also std::swap(std::set) specializes the std::swap algorithm (function template) http://cppreference.com 2022.07.31 std::set::swap(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Complexity | Example | Output: | See also
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