DSA · Theory

Postfix deferred queue

Theory

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Postfix deferred queue sits in a lab printer. Arun’s job is print jobs. Write that first.

Postfix deferred queue on the board — enqueue / dequeue FIFO. Then say what print jobs looks like after.

Skip Postfix deferred queue and confusing front and rear shows up in a lab printer.

Arun ships Postfix deferred queue in a lab printer. That is the use case worth saying.

Postfix deferred queue trap — confusing front and rear. Arun loses marks for that every viva.

After Postfix deferred queue, Arun should still remember confusing front and rear.

One breath for Postfix deferred queue, then print jobs, then confusing front and rear. Sit down.

Diagram

  front → [A][B][C] ← rear
  out ↑         ↑ in
       FIFO

Exam tip

Say Postfix deferred queue in one breath, then enqueue / dequeue FIFO, then confusing front and rear.

from collections import deque

q = deque()
q.append(10)      # enqueue
q.append(20)
print(q.popleft())  # 10
print(list(q))

Postfix deferred queue — queue is FIFO. deque.popleft() is O(1).