Block coding interview
questions, leaked.
14 problems reported across recent Block interviews. Top patterns: array, string, hash table. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Block pulls heavily from array and string manipulation, but don't mistake that for easy. Out of 14 problems in their pipeline, 9 are medium and 4 are hard. You'll face design problems that ask you to build real systems (text editors, robots, tries) alongside classic array rotations and hash-table counting. One easy problem won't save you. The assessment is medium-to-hard, pattern-heavy, and unforgiving on implementation speed. StealthCoder runs invisibly during the OA as your backup if you hit a wall on a trie or matrix problem you didn't have time to drill.
Top problems at Block
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Rotating the Box | MEDIUM | 100.0 | 79% | Array · Two Pointers · Matrix |
| 02 | Walking Robot Simulation II | MEDIUM | 97.8 | 25% | Design · Simulation |
| 03 | Count Nice Pairs in an Array | MEDIUM | 97.8 | 49% | Array · Hash Table · Math |
| 04 | Number of Black Blocks | MEDIUM | 97.8 | 39% | Array · Hash Table · Enumeration |
| 05 | Word Break | MEDIUM | 97.8 | 48% | Array · Hash Table · String |
| 06 | Pancake Sorting | MEDIUM | 97.8 | 71% | Array · Two Pointers · Greedy |
| 07 | Available Captures for Rook | EASY | 97.8 | 70% | Array · Matrix · Simulation |
| 08 | Falling Squares | HARD | 97.8 | 46% | Array · Segment Tree · Ordered Set |
| 09 | Squirrel Simulation | MEDIUM | 97.8 | 57% | Array · Math |
| 10 | Design a Text Editor | HARD | 76.2 | 47% | Linked List · String · Stack |
| 11 | Implement Trie (Prefix Tree) | MEDIUM | 69.5 | 68% | Hash Table · String · Design |
| 12 | Integer to English Words | HARD | 60.0 | 34% | Math · String · Recursion |
| 13 | The Maze | MEDIUM | 60.0 | 60% | Array · Depth-First Search · Breadth-First Search |
| 14 | Word Search II | HARD | 60.0 | 37% | Array · String · Backtracking |
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 Block OA. The proctor cannot see it. Screen share cannot detect it. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoder- array10 · 71%
- string5 · 36%
- hash table4 · 29%
- matrix4 · 29%
- design3 · 21%
- simulation3 · 21%
- trie3 · 21%
- math3 · 21%
- two pointers2 · 14%
- linked list1 · 7%
Arrays dominate with 10 appearances, followed by strings (5), hash tables (4), and matrices (4). That means you're solving rotation, enumeration, and simulation problems at scale. Design questions (3) are your surprise. Implement Trie, Design a Text Editor, and Walking Robot Simulation II aren't algorithms you can fake in five minutes. Two-pointers and greedy show up twice, so don't skip Pancake Sorting. The hard tier (Falling Squares, Design a Text Editor, Integer to English Words, Word Search II) punishes slow thinking and sloppy data structures. Drill arrays and hash tables first because they're the foundation for everything else. If you blank on Word Search II or a segment-tree variant mid-OA, StealthCoder surfaces the working approach in seconds, invisible to the proctor.
Companies with similar patterns
If you prepped for Block, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Block.
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 for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Block interview FAQ
How many array problems should I solve before the Block OA?+
Array appears in 10 of 14 problems and overlaps with almost every other topic. Solve at least one from each pattern: rotation, enumeration, sorting. Rotating the Box and Pancake Sorting are both medium; master those two and you've covered the basics.
Is design experience required for Block's assessment?+
Design problems appear 3 times and are locked at medium-to-hard difficulty. Design a Text Editor is explicitly hard. If you haven't built a trie or a stateful object before, start there. Linked lists and stacks are the backbone.
What should I prioritize if I have one week?+
Arrays and hash tables first (14 combined appearances). Then string problems (5) because they often pair with tries and arrays. Spend day 5 on design: Implement Trie and Walking Robot Simulation II. Design problems are slow to code and high-confidence if you've practiced them.
How hard are Block's problems compared to LeetCode medium?+
9 of 14 are medium, but they're not trivial medium. Word Break and Word Search II require dynamic programming and backtracking. The hard tier includes segment trees and recursive string parsing. Expect medium problems to take 20-30 minutes if you're still warming up.
Should I learn tries before the OA?+
Trie appears 3 times and is used in Word Break, Implement Trie, and Word Search II. Yes, learn tries. All three problems are achievable if you understand prefix-tree insertion and search. Skipping tries here costs you 20% of the assessment.