C++ Queue Library - empty() Function

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Description

The C++ function std::queue::empty() tests whether queue is empty or not. Queue of zero size is considered as empty queue.

Declaration

Following is the declaration for std::queue::empty() function form std::queue header.

C++98

bool empty() const;

Parameters

None

Return value

Returns true if queue is empty otherwise false.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::queue::empty() function.

#include <iostream>
#include <queue>

using namespace std;

int main(void) {
   queue<int> q;

   if (q.empty())
      cout << "Queue is empty." << endl;

   q.push(10);

   if (!q.empty())
      cout << "Queue is not empty." << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Queue is empty.
Queue is not empty.