BlackRock coding interview
questions, leaked.
17 problems reported across recent BlackRock interviews. Top patterns: array, dynamic programming, string. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
BlackRock's coding assessment hits you with 17 problems across medium and hard difficulty, and the distribution is brutal: 11 of them revolve around arrays, with dynamic programming showing up in 7. You're looking at problems like Find the Maximum Sum of Node Values, Maximum Profit From Trading Stocks, and Coin Change. The good news: it's almost all array and DP. The catch: you need to drill fast and recognize patterns cold. If you freeze on a DP formulation mid-assessment, StealthCoder runs invisible during the live OA and surfaces a working solution in seconds.
Top problems at BlackRock
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Happy Number | EASY | 100.0 | 58% | Hash Table · Math · Two Pointers |
| 02 | Valid Parentheses | EASY | 94.0 | 42% | String · Stack |
| 03 | Evaluate Division | MEDIUM | 82.3 | 63% | Array · String · Depth-First Search |
| 04 | Find the Maximum Sum of Node Values | HARD | 73.2 | 70% | Array · Dynamic Programming · Greedy |
| 05 | Maximum Subtree of the Same Color | MEDIUM | 71.4 | 57% | Array · Dynamic Programming · Tree |
| 06 | Pairs of Songs With Total Durations Divisible by 60 | MEDIUM | 71.4 | 53% | Array · Hash Table · Counting |
| 07 | Best Time to Buy and Sell Stock | EASY | 58.6 | 55% | Array · Dynamic Programming |
| 08 | Group Anagrams | MEDIUM | 58.6 | 71% | Array · Hash Table · String |
| 09 | Path with Maximum Probability | MEDIUM | 49.2 | 65% | Array · Graph · Heap (Priority Queue) |
| 10 | Maximum Profit From Trading Stocks | MEDIUM | 49.2 | 47% | Array · Dynamic Programming |
| 11 | Maximize Greatness of an Array | MEDIUM | 41.7 | 59% | Array · Two Pointers · Greedy |
| 12 | Valid Anagram | EASY | 41.7 | 67% | Hash Table · String · Sorting |
| 13 | Boundary of Binary Tree | MEDIUM | 41.7 | 47% | Tree · Depth-First Search · Binary Tree |
| 14 | Coin Change | MEDIUM | 41.7 | 46% | Array · Dynamic Programming · Breadth-First Search |
| 15 | Generate Parentheses | MEDIUM | 41.7 | 77% | String · Dynamic Programming · Backtracking |
| 16 | Longest Palindromic Substring | MEDIUM | 41.7 | 36% | Two Pointers · String · Dynamic Programming |
| 17 | Number of Islands | MEDIUM | 41.7 | 62% | Array · Depth-First Search · Breadth-First Search |
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 BlackRock OA. The proctor cannot see it. Screen share cannot detect it. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoder- array11 · 65%
- dynamic programming7 · 41%
- string6 · 35%
- hash table4 · 24%
- depth first search4 · 24%
- sorting4 · 24%
- two pointers3 · 18%
- breadth first search3 · 18%
- tree3 · 18%
- union find2 · 12%
Arrays dominate BlackRock's assessment. Eleven of the seventeen problems test your ability to manipulate sequences, which means sorting, two-pointer sweeps, and hash-table lookups become your bread and butter. Dynamic programming is the second pillar, appearing in seven problems, so expect optimization challenges where greedy won't cut it. Strings matter too, but as a secondary pattern. Depth-first search and breadth-first search each appear in three to four problems, mostly nested inside graph and tree questions. Start with array and DP problems like Best Time to Buy and Sell Stock and Coin Change. If you haven't internalized the DP recurrence for stock trading or coin-change scenarios by interview day, StealthCoder is your safety net for the live assessment when muscle memory fails.
Companies with similar patterns
If you prepped for BlackRock, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass BlackRock.
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. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
BlackRock interview FAQ
Should I spend more time on arrays or dynamic programming?+
Arrays. Eleven of seventeen problems test array skills directly. Master sorting, two-pointer partitioning, and hash-table pairing first. Then layer DP on top: most of the hard DP questions here (stock trading, coin change, node value maximization) require you to iterate through arrays efficiently. Nail arrays, then DP becomes the optimization step.
Do I need to study graph algorithms for BlackRock?+
Evaluate Division and Path with Maximum Probability are graph problems, but they're medium difficulty and account for only two problems. Union-find and shortest-path algorithms appear in roughly two problems each. They're not the priority. Drill arrays and DP first, then graph algorithms as a hedge if you have time.
How many dynamic programming problems should I solve to be ready?+
Seven problems in BlackRock's pool use DP, and they span three patterns: stock trading, coin change, and tree optimization. Solve at least five to ten classic DP problems in each category. If you can write Coin Change, Maximum Profit, and Find the Maximum Sum of Node Values from scratch, you're covered for pattern recognition during the assessment.
What's the hardest problem I'll face, and how do I prepare for it?+
Find the Maximum Sum of Node Values is the only hard problem reported. It combines array, DP, tree, and bit manipulation. Start by solving medium DP problems like Coin Change and Maximum Profit until you're comfortable with recurrence relations. Then study tree traversal with DFS. This problem isn't about a single algorithm; it's about combining techniques under pressure.
Are string problems worth studying for BlackRock?+
String problems account for six of seventeen, mostly medium difficulty. Valid Parentheses, Group Anagrams, and Generate Parentheses are classics. Study them after you've locked down arrays and DP, but don't skip them. String manipulation often pairs with hash tables and sorting, both of which show up frequently.