DSA · Theory

Queue

Theory

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Queue is a DSA idea you prove with print jobs, not with a slogan.

Queue order — meaning → enqueue / dequeue FIFO → one limit. Dumping ten features helps nobody.

Without Queue, a lab printer gets messy and print jobs is hard to trust.

Use Queue when print jobs must stay clear. If a simpler DSA step works, use that instead.

Don’t do this with Queue — confusing front and rear. Interviewers spot it in ten seconds.

Place Queue next to nearby DSA work — enqueue / dequeue FIFO is the link.

Viva for Queue — what it is → enqueue / dequeue FIFO → the mistake (confusing front and rear).

Diagram

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

Exam tip

Board: print jobs. Dry-run Queue. Name the trap: confusing front and rear.

from collections import deque

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

Queue is FIFO. deque.popleft() is O(1).