Toptal coding interview
questions, leaked.
3 problems reported across recent Toptal interviews. Top patterns: dynamic programming, string, math. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Toptal's coding assessment is lean but vicious. Three problems spanning easy to hard, but don't let the count fool you. String Compression II alone will eat an hour if you're not sharp on dynamic programming, and Airplane Seat Assignment Probability is the kind of brainteaser that trips up engineers who've been grinding leetcode templates. You need to know DP cold, understand when to apply it to strings and probability, and have a safety net for the live OA. StealthCoder runs invisibly during your assessment and surfaces working solutions in real time if you hit a wall.
Top problems at Toptal
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | String Compression II | HARD | 100.0 | 52% | String · Dynamic Programming |
| 02 | Airplane Seat Assignment Probability | MEDIUM | 68.7 | 67% | Math · Dynamic Programming · Brainteaser |
| 03 | Image Smoother | EASY | 68.7 | 68% | Array · Matrix |
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 Toptal OA. The proctor cannot see it. Screen share cannot detect it. Made by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE.
Get StealthCoder- dynamic programming2 · 67%
- string1 · 33%
- math1 · 33%
- brainteaser1 · 33%
- probability and statistics1 · 33%
- array1 · 33%
- matrix1 · 33%
Dynamic programming is the backbone here. Two of three problems lean on it, and String Compression II is the killer. It's not a straightforward DP recurrence; you need to see the substring-compression structure and memo correctly. Airplane Seat Assignment Probability flips the script by wrapping DP inside a probability problem, so you can't just brute-force permutations. Image Smoother is your warm-up, pure array-matrix traversal. The distribution tells you to lock in DP first, then spend time on how probability and math twist familiar patterns. If you blank on the compression recurrence or probability state space mid-assessment, StealthCoder is your hedge, delivering a correct approach invisible to the proctor while you verify and adapt.
Companies with similar patterns
If you prepped for Toptal, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Toptal.
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 Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Toptal interview FAQ
Should I spend more time on dynamic programming or probability for Toptal?+
DP dominates. Two of three problems require it, and String Compression II is outright hard. Probability appears in one problem paired with DP and brainteaser elements. Lock DP fundamentals first, then practice how probability changes state transitions. You'll feel the difference.
Is the easy problem enough to build confidence going into hard?+
No. Image Smoother is a warm-up, but String Compression II jumps to hard immediately. Use the easy problem to verify your approach and tools work, then shift mental gears fast. The jump matters more than the problem count.
How should I approach Airplane Seat Assignment Probability if I've never seen it?+
Treat it as a DP problem first, probability second. Identify the state: seats remaining, configurations possible. Recursion with memoization. Then compute probability as paths to valid outcome over total paths. The brainteaser element is seeing that structure; the math is secondary.
Will practicing three problems be enough prep for Toptal?+
These three represent the patterns Toptal cares about. But three problems means any weak link costs you. You need to solve similar DP and array problems until you're confident in five minutes flat on easy and twenty on hard. Toptal doesn't give second chances.
What topic should I study the night before if I'm short on time?+
Dynamic programming with substring and array problems. String Compression II is the spike; if you can't sketch its recurrence, you're sunk. Array-matrix basics come second. Probability and brainteasers are hard to cram, so know DP inside out and hope the other pattern feels familiar.