Build Blocks and Obstacles
Reported by candidates from Uber's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
You're facing Uber's "Build Blocks and Obstacles" problem in August 2024, and you have no verbatim text to study. That's actually the position most candidates are in right now. The problem title suggests a grid or construction mechanic. You're probably building something while navigating constraints. StealthCoder reads the live problem and feeds you the pattern in real time, so you're not guessing blind in the assessment. Treat the next 48 hours as pattern recognition, not memorization.
Pattern and pitfall
Grid-based problems at Uber typically involve pathfinding, state tracking, or simulation. "Build Blocks and Obstacles" hints at either a construction/placement puzzle (greedy or dynamic programming to optimize placement) or a traversal problem where you're moving through a space with movable or fixed barriers. The real trick is usually in recognizing whether you're optimizing placement, count, or path. Most candidates miss the constraint that blocks and obstacles behave differently under the rules. You'll need to clarify the problem statement instantly in the OA. StealthCoder becomes your safety net if you freeze on the exact mechanics. Focus on reading the input format and constraints first, then build a simple simulation or BFS solution. Avoid jumping to complex DP unless the problem explicitly asks for optimization across multiple states.
StealthCoder is the hedge for the one pattern you didn't drill. It runs invisibly during the screen share.
You can drill Build Blocks and Obstacles cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. If you're reading this with an OA window open, you're who this was built for.
Get StealthCoderRelated leaked OAs
You've seen the question.
Make sure you actually pass Uber's OA.
Uber reuses patterns across OAs. If you're reading this with an OA window open, you're who this was built for. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Build Blocks and Obstacles FAQ
Is this a pathfinding problem or a placement/construction problem?+
Without the full text, both are possible. Pathfinding usually asks "can you reach X" or "find shortest path." Placement asks "how many blocks fit" or "minimize obstacles." Read the problem statement carefully. The first line and constraints tell you which bucket this is in.
How hard are Uber grid problems compared to LeetCode medium?+
Uber grid problems sit in the medium-to-hard range, usually asking for BFS, DFS, or greedy logic with a twist. This one's title doesn't scream brute force, so expect a constraint or optimization rule that rewards clean thinking over raw recursion.
What's the most common mistake on grid construction problems?+
Treating blocks and obstacles as identical. They're usually not. Blocks are things you place or stack. Obstacles are things that block movement or placement. Read the rules for how each behaves under the problem's mechanics.
Do I need to precompute anything before the OA?+
Memorize BFS template (queue, visited set, four-direction loop) and basic DFS. Both run in O(n*m) on grids. That covers 80% of grid problems. Have a simulation template ready too, since "building" often means step-by-step state updates.
How do I prepare for a problem I can't see the full text for?+
You don't prep the specific problem. You prep the pattern. Study BFS, DFS, greedy placement, and state simulation. Read the Uber problem the moment the OA starts. The first 2-3 minutes of reading is worth more than an hour of blind guessing.