Maximum Cells
Reported by candidates from Microsoft's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Microsoft's Maximum Cells question has shown up in assessments since June 2024, and it's a grid problem that looks simple but trips up candidates who don't see the real constraint. You're likely looking at a matrix traversal or counting problem where the naive approach times out. The trick is almost always about either greedy selection, dynamic programming, or recognizing a mathematical pattern that collapses the search space. StealthCoder can catch you if you freeze on the optimal order of operations.
Pattern and pitfall
Without the exact problem text, the pattern for 'Maximum Cells' problems typically hinges on either maximizing reachable cells in a grid (BFS/DFS with pruning), or selecting the largest subset of cells under some constraint (greedy or DP). Microsoft leans toward problems where the constraint is implicit: you can't visit the same cell twice, or movement is restricted to specific directions. The catch is that a brute-force cell enumeration will fail. You need to either find a formula (math), or recognize that the optimal selection follows a greedy pattern (take the largest available, exclude neighbors). If it's a counting problem, prefix sums or memoization will accelerate the answer. StealthCoder sees the pattern live and suggests the right traversal order before you waste time.
StealthCoder is the hedge for the one pattern you didn't drill. It runs invisibly during the screen share.
You can drill Maximum Cells 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.
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Maximum Cells FAQ
Is this a grid traversal or a selection problem?+
Most likely grid traversal with a twist. You're probably finding the maximum number of cells you can visit or mark under a constraint, not just counting all cells. The constraint is what kills the naive approach.
Will BFS or DFS alone get me there?+
Not in the fast lane. Standard traversal is a building block, but you need to layer in either greedy logic (pick the best cell at each step) or memoization to avoid recomputing subproblems. Microsoft doesn't accept O(n^2) or worse for grid problems.
What's the most common pitfall?+
Forgetting that visited cells block future moves. Candidates often iterate all cells and assume each is independent. They're not. Once you pick a cell, its neighbors or region becomes invalid. Track state carefully.
How do I solve this in under 40 minutes?+
Sketch the small example and trace what 'maximum' means. Is it area, count, or distance? Then code a single-pass greedy or DP solution. Test edge cases: empty grid, single cell, fully blocked. Don't optimize prematurely.
Is this still asked by Microsoft in 2024?+
Yes. Reported in June 2024. Grid and matrix problems are core to Microsoft OAs. Expect minor variations on direction rules or cell types, but the logic remains: traverse smart, not brute-force.