//queue STL

//queue is just a container adaptor, which is a class that use other container.

//just like stack

q1.push(x)     //push x into the queue

q1.pop()        //pop the first element in the queue

q1.front()       //return the first element in the queue

q1.back()        //return the last element in the queue

q1.empty()

q1.size()

//C++11

q1.emplace(x)    //add a new element at the end of the queue, after its current last element 

//the differences between emplace and push

//though they are both the functions to add elements in the queue

//if you use emplace ,you will not make a new class.

//Let's see a example

struct node

{

	int x, y;

	node(int a, int b) :x(a), y(b){}

};

int main()

{

	queue<node>q1,q2;

	q1.emplace(1, 2);

	q2.push(node(1, 2));

	cout << q1.front().x << endl;

	return 0;

}