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std::unordered_map::empty(3) C++ Standard Libary std::unordered_map::empty(3) NAME std::unordered_map::empty - std::unordered_map::empty Synopsis bool empty() const noexcept; (since C++11) (until C++20) [[nodiscard]] bool empty() const noexcept; (since C++20) Checks if the container has no elements, i.e. whether begin() == end(). Parameters (none) Return value true if the container is empty, false otherwise Complexity Constant. Example The following code uses empty to check if a std::un- ordered_map<int,int> contains any elements: // Run this code #include <unordered_map> #include <iostream> #include <utility> int main() { std::unordered_map<int, int> numbers; std::cout << std::boolalpha; std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n'; numbers.emplace(42, 13); numbers.insert(std::make_pair(13317, 123)); std::cout << "After adding elements, numbers.empty(): " << num- bers.empty() << '\n'; } Output: Initially, numbers.empty(): true After adding elements, numbers.empty(): false See also size returns the number of elements (C++11) (public member function) empty checks whether the container is empty (C++17) (function template) http://cppreference.com 2022.07.31 std::unordered_map::empty(3)
NAME | Synopsis | Parameters | Return value | Complexity | Example | Output: | See also
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