std::set::empty

From cppreference.com

< cpp‎ | container‎ | set

bool empty() const;

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

Contents

[edit] Parameters

(none)

[edit] Return value

true if the container is empty, false otherwise

[edit] Exceptions

(none)	(until C++11)
`noexcept` specification: noexcept	(since C++11)

[edit] Complexity

Constant.

[edit] Example

The following code uses empty to check if a std::set<int> contains any elements:

Run this code

#include <set>
#include <iostream>
 
int main()
{
    std::set<int> numbers;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
 
    numbers.insert(42);
    numbers.insert(13317); 
    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)

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unconditionally noexcept