C++ queue - empty() Function

The C++ queue::empty function is used to check whether the queue is empty or not. It returns true if the size of the queue is zero, else returns false.

Syntax

C++98
C++11

bool empty() const;

bool empty() const noexcept;

Parameters

No parameter is required.

Return Value

true if the size of the queue is zero, else returns false.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the queue::empty function is used to check whether the queue is empty or not.

#include <iostream>
#include <queue>
using namespace std;
 
int main (){
  queue<int> MyQueue;

  cout<<boolalpha;

  cout<<"Is the Queue empty?: "<<MyQueue.empty()<<"\n";

  cout<<"Add elements in the Queue.\n";
  MyQueue.push(10);
  MyQueue.push(20);
  MyQueue.push(30);

  cout<<"Now, Is the Queue empty?: "<<MyQueue.empty()<<"\n";
  return 0;
}

The output of the above code will be:

Is the Queue empty?: true
Add elements in the Queue.
Now, Is the Queue empty?: false

❮ C++ <queue> Library