Queue

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

q.add(10);

q.add(20);

q.add(30);

System.out.print(q.poll() + " ");

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

• 10 20

• 20 30

• 10 30

• Error

Which operation is possible in a Deque?

• Insert only at front

• Insert only at rear

• Insert/Delete at both ends

• Only delete

Deque<Integer> dq = new ArrayDeque<>();

dq.offerFirst(1);

dq.offerLast(2);

dq.offerFirst(3);

dq.pollLast();

dq.offerLast(4);

dq.pollFirst();

System.out.print(dq);

• [1, 4]

• [2, 4]

• [3, 2]

• [1, 2]

PriorityQueue<Integer> pq = new PriorityQueue<>();

pq.add(7);

pq.add(2);

pq.add(9);

pq.add(1);

pq.remove(7);

System.out.print(pq.poll());

• 1

• 2

• 7

• 9

Deque<Integer> dq = new ArrayDeque<>();

dq.add(10);

dq.add(20);

dq.add(30);

Iterator<Integer> it = dq.descendingIterator();

while(it.hasNext())

System.out.print(it.next()+" ");

• 10 20 30

• 30 20 10

• Random order

• Error

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

q.add(3);

q.add(1);

q.add(2);

while(!q.isEmpty())

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

• 312

• 123

• 231

• Random

PriorityQueue<Integer> pq = new PriorityQueue<>();

pq.add(5);

pq.add(2);

pq.add(8);

pq.add(1);

System.out.print(pq.poll() + " ");

pq.add(0);

System.out.print(pq.poll());

• 1 0

• 1 2

• 2 0

• 0 1