Salesforce·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Salesforce software engineering interview with a linked list problem that had two parts. Pretty straightforward conceptually but the complexity analysis at the end is where things get interesting.

Questions Asked (1)

Given a linked list, remove duplicates so each value appears only once. Walk through your approach for both sorted and unsorted versions, and analyze the time and space complexity of each.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The sorted case felt manageable.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: confirm whether the linked list is sorted or unsorted, as the approach differs. For sorted lists, use a two-pointer technique to remove duplicates in O(n) time and O(1) space. For unsorted lists, use a hash set to track seen values, which takes O(n) time and O(n) space. Walk through each approach step-by-step, analyze complexities, and discuss trade-offs.

Pro tip: Mention that for unsorted lists, if memory is a constraint, you could sort the list first (O(n log n) time) and then remove duplicates in O(n) time with O(1) space, but this modifies the original order. This shows you consider trade-offs beyond the obvious.

1. Clarify the problem

Ask if the linked list is sorted or unsorted, and whether we can modify the list in place or need to preserve order. Also confirm if we need to return the head of the modified list.

2. Sorted list approach

Traverse the list with a pointer, comparing each node's value with the next. If duplicate, remove the next node by adjusting pointers. Continue until end. Time O(n), space O(1).

3. Unsorted list approach

Use a hash set to track seen values. Traverse the list, and for each node, if its value is in the set, remove it; otherwise, add to set. Time O(n), space O(n).

4. Analyze complexities and trade-offs

Compare the two approaches: sorted is more efficient in space but requires sorted input; unsorted uses extra space but works for any list. Discuss alternative: sort first then remove duplicates, but note it changes order and takes O(n log n) time.

5. Test with examples

Walk through a simple example for each case, e.g., sorted: 1->1->2->3->3; unsorted: 3->1->2->1->3. Show how pointers or set are updated.

Key Points to Mention

Time and space complexity for each approach: sorted O(n) time O(1) space; unsorted O(n) time O(n) space.
Edge cases: empty list, single node, all duplicates, no duplicates.
Pointer manipulation details: how to remove a node by updating next pointers.
Hash set usage: checking membership and adding values.
Trade-offs: memory vs. time, and whether modifying the list is acceptable.
Alternative approach: sorting first for unsorted lists, but note it changes order and adds O(n log n) time.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.