std::vector<T,Allocator>::empty

From cppreference.com
< cpp‎ | container‎ | vector

 
 
 
 
bool empty() const;
(until C++11)
bool empty() const noexcept;
(since C++11)
(until C++20)
[[nodiscard]] constexpr 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

#include <vector>
#include <iostream>
 
int main()
{
    std::cout << std::boolalpha;
    std::vector<int> numbers;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
 
    numbers.push_back(42);
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

Output:

Initially, numbers.empty(): true
After adding elements, numbers.empty(): false

See also

returns the number of elements
(public member function)
(C++17)
checks whether the container is empty
(function template)