std::map::empty
From cppreference.com
| bool empty() const; |
(until C++11) | |
| 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::map<int, int> contains any elements:
Run this code
#include <map> #include <iostream> #include <utility> int main() { std::map<int,int> numbers; 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(): " << numbers.empty() << '\n'; }
Output:
Initially, numbers.empty(): 1 After adding elements, numbers.empty(): 0
See also
| returns the number of elements (public member function) |