What is the difference between a stack and a queue, and when would you choose one over the other?

technical-conceptual · Junior level · software-engineering

What the interviewer is really asking

Assesses foundational knowledge of data structures and ability to match the right tool to a problem.

What to say

• Explain LIFO (stack) vs FIFO (queue) with simple concrete analogies — a call stack vs a print queue.
• Give a real use case for each: stack for undo/redo or DFS traversal, queue for BFS or task scheduling.
• Mention that both have O(1) push/pop or enqueue/dequeue in typical implementations.

What to avoid

• Confuse the two or say one is strictly 'better' without context.
• Only describe them abstractly without linking to a real use case.
• Claim stacks are arrays and queues are linked lists as if that's a hard rule.

Example answers

Strong: A stack is perfect for tracking browser history — the back button pops the most recent page. A queue works well for processing incoming web requests in the order they arrived.

Weak: A stack is FIFO, right? Or maybe that's a queue — I'd need to look it up before using one in code.