C++ <deque> - empty() Function

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

Time Complexity

Constant i.e, Θ(1).

Example:

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

#include <iostream>
#include <deque>
using namespace std;
 
int main (){
  deque<int> MyDeque;

  cout<<boolalpha;

  cout<<"Is the Deque empty?: "<<MyDeque.empty()<<"\n";

  cout<<"Add elements in the Deque.\n";
  MyDeque.push_back(10);
  MyDeque.push_back(20);
  MyDeque.push_back(30);

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

The output of the above code will be:

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

❮ C++ <deque> Library