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std::queue<T,Container>::empty

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

Checks if the underlying container has no elements, i.e. whether c.empty().

Parameters

(none).

Return value

true if the underlying container is empty, false otherwise.

Complexity

Constant.

Example

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

Output:

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

See also

returns the number of elements
(public member function)

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