HubSpot Coding Interview Questions
25 HubSpot coding interview problems with full optimal solutions — 8 easy, 12 medium, 5 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an HubSpot interviewer values, and a FAQ section.
Showing 12 problems of 25
- #3mediumfrequently asked
3. Longest Substring Without Repeating Characters
HubSpot uses this sliding-window classic to test both the pattern itself and your ability to manage a moving window's state efficiently — directly applicable to deduplicating streaming event logs in their CRM activity feeds.
- #15mediumfrequently asked
15. 3Sum
HubSpot asks 3Sum to test your ability to reduce a multi-pointer problem systematically — a key skill when de-duplicating and reconciling overlapping data records across their CRM's contact merge workflows.
- #49mediumfrequently asked
49. Group Anagrams
HubSpot frequently asks Group Anagrams because it tests canonical key generation for grouping — a fundamental skill in CRM data normalization where contacts or properties with different surface strings need to be clustered by canonical form.
- #56mediumfrequently asked
56. Merge Intervals
HubSpot asks Merge Intervals because overlapping-range problems appear constantly in their scheduling, deal-stage overlap detection, and meeting de-duplication workflows — and they want to see clean sort-then-scan logic with tight boundary handling.
- #98mediumfrequently asked
98. Validate Binary Search Tree
HubSpot asks Validate BST to test whether you understand the BST property beyond the naive 'left < root < right' check — they want to see you propagate valid range bounds through the recursion, a pattern that reflects the kind of constraint-passing thinking their backend engineers apply daily.
- #139mediumoccasionally asked
139. Word Break
HubSpot uses Word Break to test bottom-up dynamic programming and substring reachability — reasoning patterns that map directly to parsing HubSpot's expression language and evaluating segmented workflow conditions.
- #146mediumfrequently asked
146. LRU Cache
HubSpot asks LRU Cache because it's a real design problem embedded in a coding question — their platform caches CRM data aggressively, and engineers are expected to understand how eviction policies are implemented, not just configured.
- #200mediumfrequently asked
200. Number of Islands
HubSpot asks Number of Islands to test graph traversal fundamentals — BFS and DFS on an implicit grid — skills that transfer to connected-component analysis in their contact relationship graph and account hierarchy features.
- #207mediumoccasionally asked
207. Course Schedule
HubSpot asks Course Schedule to assess cycle detection in directed graphs — a pattern that arises in their workflow automation engine where circular dependency detection between triggers and actions is a critical correctness guarantee.
- #238mediumfrequently asked
238. Product of Array Except Self
HubSpot includes this problem to test prefix/suffix product reasoning without division — a constraint that forces you to think about the problem from two directions simultaneously, a hallmark of the kind of algorithmic clarity their Boston engineering team values.
- #322mediumoccasionally asked
322. Coin Change
HubSpot uses Coin Change to probe unbounded knapsack / bottom-up DP thinking — the same pattern that underlies their pricing-plan composer and subscription credit allocation logic, where achieving an exact amount from discrete denominations matters.
- #347mediumfrequently asked
347. Top K Frequent Elements
HubSpot asks Top K Frequent Elements to test your knowledge of heap-based selection and bucket sort — patterns that power ranking and analytics features like 'top properties by usage' or 'most engaged contacts' across their marketing platform.
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