Technical interview guide

Linked Lists

Singly/doubly linked lists, pointer manipulation, and the classic two-pointer patterns.

Read: 40 min
Practice MCQs: 25
Interview QA: 25
Edition: v6
Editorial status: Reviewed
Relevant for: AI EngineerBackend EngineerBlockchain DeveloperComputational BiologistData ScientistEmbedded Systems EngineerFrontend EngineerFull-Stack DeveloperMachine Learning EngineerQuantum Software EngineerRobotics EngineerSoftware Engineer

Scope: Language-neutral, with container behaviour cited from CPython 3.14, the C++ standard containers, and java.util as of Java 21.

Interview QA

Treat each question like a live interview question: answer out loud first (structure, assumptions, tradeoffs), then open the model answer to spot gaps and rehearse a tighter follow-up.

Curated: 2026-10-05 · Written: 2026-10-05 · Reviewed: 2026-10-03

QA-1

Explain what a linked list actually buys and how it changes a production decision.

QA-2

How would you reason about why arrays usually win in practice in a system you own?

QA-3

Walk through the dummy head node, including where engineers most often get it wrong.

QA-4

What does iterative reversal guarantee, and what does it deliberately leave open?

QA-5

Describe recursive reversal and its cost and the evidence you would collect before relying on it.

QA-6

How do you reverse a sublist of a singly linked list from position m to n in-place in one pass?

QA-7

Where does deleting a node matter, and where is it irrelevant?

QA-8

How do you detect if a linked list has a cycle using O(1) auxiliary space, and how do you locate the cycle's starting node?

QA-9

What are the time and space complexity trade-offs between tracking visited nodes with a hash set versus Floyd's tortoise and hare algorithm for cycle detection?

QA-10

How do you find the node where two singly linked lists intersect in O(N + M) time and O(1) auxiliary space?

QA-11

What would you measure before treating finding the intersection of two lists as settled?

QA-12

How does merging two sorted lists change if the workload grows by two orders of magnitude?

QA-13

A vendor promises merge sort on a linked list is handled for you. What do you still own?

QA-14

When would you refuse a design because of splitting a list in half?

QA-15

How would you explain doubly linked lists without using the usual slogan?

QA-16

What failure would you inject to check a team's understanding of circular lists and sentinels?

QA-17

How should on-call treat an alert that names the LRU cache structure as the cause?

QA-18

What belongs in a runbook section on intrusive lists, and what does not?

QA-19

How would you review a pull request whose risk is memory overhead per element?

QA-20

What trade-off does unrolled lists and deques force that a junior answer usually skips?

QA-21

How would you brief product on why recursion over lists delays a ship date?

QA-22

What is the smallest experiment that would change your mind about in-place versus copying?

QA-23

How does testing pointer manipulation interact with rollback, and where do people ignore that?

QA-24

What would you ask a candidate who recites detecting corruption but cannot apply it?

QA-25