size

Header

size_type size() const

Returns the number of objects stored in the queue at a given time.

Sample

//Compiler options: /GX

#include <queue>
#include <iostream>

int main()
{
	std::queue<int> qi ; //Constructs an empty queue, uses deque as default container.

	int i ;

	std::queue<int>::allocator_type a1 = qi.get_allocator() ;

	std::cout << "call qi.empty()" << std::endl ;

	if (qi.empty())
	{
		std::cout << "queue is empty" << std::endl ;
	}
	else
	{
		std::cout << "queue contains some elements" << std::endl ;
	}

	std::cout << "qi.size() = " << qi.size() << std::endl ;

	std::cout << "Push Values on qi = " ;
	for(i = 0; i < 10; i++)
	{
		std::cout << i << ", " ;
		qi.push(i) ;
	}
	std::cout << std::endl ;
	std::cout << "qi.size() = " << qi.size() << std::endl ;
	std::cout << "Pop Values from qi = " ;
	while (!qi.empty())
	{
		std::cout << qi.front() << ", " ;
		qi.pop() ;
	}

	std::cout << std::endl ;
	
	return 0 ;
}

Program Output

call qi.empty()
queue is empty
qi.size() = 0
Push Values on qi = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
qi.size() = 10
Pop Values from qi = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,