ITPEC FE Morning April 2023 Question 8

Queue (FIFO) operation trace — track element order through enqueue/dequeue sequence.

Trace the operations on an initially empty queue:

• •ENQ 1, ENQ 2, ENQ 3 → queue: [1, 2, 3]
• •DEQ → removes 1 → [2, 3]
• •ENQ 4, ENQ 5 → [2, 3, 4, 5]
• •DEQ → removes 2 → [3, 4, 5]
• •ENQ 6 → [3, 4, 5, 6]
• •DEQ, DEQ → removes 3, then 4 → [5, 6]

Next DEQ removes 5.

Why not others:
- (a) 1 — already removed at step 4
- (b) 2 — already removed at step 7
- (d) 6 — would be removed after 5, not before

Key rule: Queue = FIFO. Elements leave in the same order they entered.

AI-generated — may contain errors