Cop
Reported by candidates from DE Shaw's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
DE Shaw's 'Cop' problem came up in March 2024 and caught candidates off guard because the title gives almost nothing away. You're staring at this 24 hours before the OA, and the problem statement is either vague or you're not sure what they're really asking for. That's the friction point. StealthCoder reads the actual problem text on your screen during the live assessment and hands you the pattern instantly. No guessing, no blank stares. You move.
Pattern and pitfall
Without the full problem text, the pattern isn't immediately clear, but 'Cop' problems at DE Shaw tend to hinge on simulation, graph traversal, or game-theory logic. The trick is usually that a straightforward greedy approach fails. You need to model the cop's movement or the game state correctly, often tracking position and rules across iterations. Many candidates burn time on the first attempt, then realize they've missed a state constraint or a rule interaction. That's where the live hedge matters. StealthCoder catches the problem structure in seconds and surfaces the actual constraint you'd have missed in the first 10 minutes solo.
The honest play: practice the pattern, and have StealthCoder ready for the one you didn't see coming.
You can drill Cop 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. Built for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play.
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DE Shaw reuses patterns across OAs. Built for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Cop FAQ
Is this a graph problem or a simulation?+
Usually both. You're modeling movement and state over time. Expect BFS or DFS to track paths, or simulation to run the game to completion. The trick is recognizing which one saves you from TLE.
What's the common mistake candidates make?+
Assuming greedy works. Most solve it once as a simple chase, then hit a test case and realize rules or boundaries change the optimal strategy. Slow down and model the full state first.
How much time should I spend on the first attempt?+
15 minutes max to outline the structure. If you're not clear on the rules by then, re-read the problem statement carefully. DE Shaw loves edge cases hiding in the wording.
Is this asked often at other companies?+
Not by that exact title. It's a DE Shaw original. But the underlying patterns (pursuit, game simulation, state tracking) show up at Google, Jane Street, and trading firms. The logic transfers.
Can I solve this in 48 hours of prep?+
Not cold. If you haven't seen simulation or pursuit problems before, you'll struggle. Best move is to review similar problems on LeetCode and trust StealthCoder to anchor you during the live OA.