Question

What’s the output of the following code?

Queue<Integer> q = new Queue<Integer>();

q.enqueue(30);

  q.dequeue();

q.enqueue(40);

q.enqueue(20);

q.dequeue();

q.enqueue(80);

System.out.print(q.dequeue());

Answer 1

$\small \color{blue}Answer:\;\;$

20

Explanation:
-------------
Queue<Integer> q = new Queue<Integer>();
q.enqueue(30);  // queue is [30], with 30 at front
q.dequeue();    // front=30 is removed, queue is [].
q.enqueue(40);  // queue is [40], with 40 at front
q.enqueue(20);  // queue is [40, 20], with 40 at front
q.dequeue();    // front=40 is removed, queue is [20].
q.enqueue(80);  // queue is [20, 80], with 20 at front
System.out.print(q.dequeue());  // front=20 is removed and printed