Template:cpp/container/map/example empty
From cppreference.com
The following code uses empty to check if a std::map<int, int> contains any elements:
Run this code
#include <iostream>
#include <map>
#include <utility>
int main()
{
std::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(): " << numbers.empty() << '\n';
}
Output:
Initially, numbers.empty(): true
After adding elements, numbers.empty(): false