DeltaX coding interview
questions, leaked.
3 problems reported across recent DeltaX interviews. Top patterns: hash table, math, string. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
DeltaX's assessment hits you with three problems across easy and medium difficulty, and the pattern is tight. Hash tables and math show up twice each, which means you're not just grinding array loops. String manipulation and math-heavy problems like Roman to Integer are table stakes. If you've spent the last week only on sliding windows and sorting, you're walking in blind. Most candidates underestimate the hash-table-plus-math combo and freeze mid-assessment. That's where StealthCoder becomes your real safety net: if a hash-table pattern doesn't click when you're live, it solves invisibly while the proctor sees you thinking.
Top problems at DeltaX
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Roman to Integer | EASY | 100.0 | 65% | Hash Table · Math · String |
| 02 | Longest Consecutive Sequence | MEDIUM | 68.6 | 47% | Array · Hash Table · Union Find |
| 03 | Different Ways to Add Parentheses | MEDIUM | 68.6 | 72% | Math · String · Dynamic Programming |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual DeltaX OA. The proctor cannot see it. Screen share cannot detect it. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoder- hash table2 · 67%
- math2 · 67%
- string2 · 67%
- array1 · 33%
- union find1 · 33%
- dynamic programming1 · 33%
- recursion1 · 33%
- memoization1 · 33%
The three problems DeltaX uses cluster around hash tables (2), math (2), and strings (2), with one medium-difficulty problem combining all three. Roman to Integer is straightforward if you've drilled it; Longest Consecutive Sequence is the trap that catches people who only know hash maps for counting. It demands union-find or a clever linear-time hash approach, and most candidates miss the optimization. Different Ways to Add Parentheses is the ceiling, mixing recursion, memoization, and dynamic programming. Your prep order: hash-table edge cases first (not just basic lookups), then math parsing, then the recursion-memoization blend. The problem set is small but dense. Don't waste time on topics outside the core four. When you hit the assessment and a DP recursion pattern doesn't materialize, StealthCoder runs in the background and you move on undetected.
Companies with similar patterns
If you prepped for DeltaX, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass DeltaX.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
DeltaX interview FAQ
How much time should I spend drilling hash-table problems before DeltaX's OA?+
Hash tables appear in 2 of 3 problems here, so make it 40-50% of your prep. Focus on Longest Consecutive Sequence specifically, which requires a non-obvious hash approach. Basic hash-map counting problems won't cut it. Hit union-find patterns too, since that problem touches both.
Is 'Roman to Integer' enough if I skip the medium problems?+
No. Roman to Integer is easy and gets you partial credit, but the two medium problems are where DeltaX filters candidates. Longest Consecutive Sequence and Different Ways to Add Parentheses have nasty edge cases and optimization surprises. You need all three.
What should I study first for DeltaX if I only have three days?+
Day 1: hash-table patterns and union-find for Longest Consecutive Sequence. Day 2: Roman numeral parsing and string-to-number conversions. Day 3: recursion with memoization for the parentheses problem. Don't skip memoization, it's half the third problem.
Do I need to know dynamic programming to pass DeltaX?+
One of the three problems uses it heavily, so yes. Different Ways to Add Parentheses is a recursion-with-memoization classic. You don't need to be an DP wizard, but you can't blank on the pattern. It's 33% of the assessment.
Should I memorize Roman numeral rules or understand the hash-table trick?+
Understand the hash-table trick. Roman to Integer uses a hash map to store symbol values, not just raw conversion logic. The hash approach is faster and cleaner. Since hash tables dominate DeltaX's problem set, practicing this pattern teaches you the mindset for the harder problems.