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

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< cpp‎ | container‎ | vector

C++
Containers library
std::vector
Member types
Member functions
Non-member functions
(until C++20) (until C++20) (until C++20) (until C++20) (until C++20)
Deduction guides(C++17)
bool empty() const;
 (noexcept since C++11)
(constexpr 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

Run this code
#include <iostream>
#include <vector>
 
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)
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