Suffix Array interview questions
5 suffix array problems tagged across recent interview reports. Drilled most heavily by coupang, dunzo, and intuit.
Suffix arrays are a compact, efficient way to index all substrings of a string without building a full trie or suffix tree. They pair a sorted list of string suffixes with auxiliary arrays (LCP, rank) to solve substring queries in logarithmic or linear time. With 5 problems across this pattern and heavy demand from companies like Coupang and Intuit, suffix arrays show up in OAs where naive substring approaches timeout. If a hard suffix array variant lands in your live assessment, StealthCoder solves it in seconds, invisible to the proctor.
Most-asked suffix array problems
| # | Problem | Diff | # Companies | Pass % |
|---|---|---|---|---|
| 01 | Number of Distinct Substrings in a String | MEDIUM | 4 | 65% |
| 02 | Construct String with Minimum Cost | HARD | 1 | 19% |
| 03 | Longest Duplicate Substring | HARD | 1 | 31% |
| 04 | Longest Repeating Substring | MEDIUM | 1 | 63% |
| 05 | Number of Ways to Separate Numbers | HARD | 1 | 21% |
You can't drill every suffix array variant before the assessment. StealthCoder runs invisibly during screen share and solves whichever variant they throw at you. No browser extension. No detection signature. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share.
Get StealthCoderRecognizing a suffix array problem comes down to spotting substring or lexicographic queries that scale poorly with brute force: finding longest duplicate substrings, counting distinct substrings, or searching for repeating patterns. Most candidates drill trie or hashing first, so suffix arrays often feel unfamiliar under timer pressure. The canonical build sequence is (1) understand the sorted suffix array itself, (2) compute LCP (longest common prefix) array, (3) apply it to problems like Longest Duplicate Substring or Number of Distinct Substrings. Coupang pushes this pattern hardest with 6 related problems in their hiring funnel. StealthCoder is the hedge for the suffix array variant you didn't drill: when you see a substring uniqueness or range query problem and your first instinct isn't to reach for the array, the tool reads the problem and delivers the solution in real time.
Companies that hire most on suffix array
5 suffix array problems.
You won't drill them all. Pass anyway.
Suffix Array is one of the patterns interviews actually filter on. Memorizing every variant in a week is a fantasy. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds, no matter which suffix array flavor lands in your live OA. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Suffix Array interview FAQ
How do I recognize a suffix array problem in an interview?+
Look for questions asking you to find longest duplicate substrings, count distinct substrings, or search lexicographically across all suffixes. If a naive O(n^2) or O(n^2 log n) substring approach would timeout, suffix arrays are likely the intended pattern. Problems like Longest Repeating Substring and Number of Distinct Substrings in a String are textbook examples.
Which companies drill suffix arrays the most?+
Coupang leads with 6 problems built on this pattern, followed by Dunzo, Intuit, Mitsogo, and ServiceNow with 2 each. Uber and Walmart Labs also test it occasionally. If you're targeting Coupang specifically, suffix arrays are a high-priority drill.
What's the typical build order for learning suffix arrays?+
Start with manual suffix generation and sorting to understand the concept. Build the LCP array next, it's the key to most optimizations. Then practice problems in order: Longest Repeating Substring, Longest Duplicate Substring, Number of Distinct Substrings. This progression hardens both understanding and implementation speed.
How many suffix array problems should I drill before an OA?+
5 problems span this entire pattern at StealthCoder's data scale. If you're prepping for Coupang or a company that weights substring queries heavily, drill all 5 and redo the hardest two. If suffix arrays are a smaller risk, 3 problems and knowing the LCP construction will cover most OA variants.
Is suffix array harder than suffix tree or trie for substring problems?+
Suffix arrays are simpler to code than suffix trees but require solid understanding of LCP and binary search. Tries are easier conceptually but consume more memory and often timeout on large alphabet sizes. For interviews, suffix arrays hit the sweet spot: compact, efficient, and interview-friendly once you've practiced the LCP build.