C++ Queue Library - queue() Function

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Description

The C++ default constructor std::queue::queue() constructs queue object. If cntr argument is passed to constructor, copy of argument is assigned to container otherwise empty queue object is created.

Declaration

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

C++98

explicit queue (const container_type& ctnr = container_type());

Parameters

ctnr − Container type which is second parameter of class template.

Return value

Constructor never returns value.

Time complexity

Linear if container of non-zero size is passed as argument otherwise constant.

Example

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

#include <iostream>
#include <queue>

using namespace std;

int main(void) {   
   deque<int> d(5, 100);
   queue<int>q1;
   queue<int> q2(d);

   cout << "Size of q1 = " << q1.size() << endl;
   cout << "Size of q2 = " << q2.size() << endl;

   return 0;
}

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

Size of q1 = 0
Size of q2 = 5