std::map::empty

 

C++

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std::map

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bool empty() const;

Checks if the container has no elements, i.e. whether begin() == end().

Parameters

(none)

Return value

true if the container is empty, false otherwise

Exceptions

noexcept specification:  

noexcept

  (since C++11)

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> 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

size	returns the number of elements (public member function)