Reverse a singly linked list iteratively and recursively
Reported in GitLab European engineering loops. Pointer manipulation staple for junior coding interviews.
Interview scenario
Often asked in GitLab loops at European offices (London, Berlin, Amsterdam, Paris, Stockholm, Dublin, and remote EU). Prepare a clear spoken answer plus key trade-offs.
Model answer
Try answering aloud first
Cover trade-offs, structure, and a concrete example before revealing the baseline response.
How to frame this at GitLab: Connect your answer to measurable impact, clarity of thought, and trade-offs the team cares about. Below is a strong baseline response you can adapt with your own project examples.
Iterative approach uses three pointers: prev, curr, next. Rewire curr.next to prev, advance all pointers until curr is null; return prev as new head.
function reverseList(head) {
let prev = null, curr = head;
while (curr) {
const next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
return prev;
}Recursive: reverse rest of list, then set head.next.next = head and head.next = null. Base case: empty or single node.
Time O(n), space O(1) iterative or O(n) recursion stack. Mention reversing in groups, palindrome check, and cycle detection (Floyd) as follow-ups.
Discussion
Comments (0)
Share how this question came up in your loop, or add tips for others preparing.
Log in to comment on this question.