D. E. Shaw Coding Interview: Core Coding Round

Four problems decide most D. E. Shaw coding rounds once you get past the format. The assessment lesson covered the timer and the DSA-patterns lesson worked a knapsack, a shortest-hop search, and a prefix count. This lesson takes the four that recur next and that neither of those touched. Trading a stock at most twice for the best profit. A max-min placement you solve by searching the answer space, not the input. Counting how out of order a list is. Finding the single links whose removal splits a network.

The D. E. Shaw angle

One of these four is the problem candidates walk out of the OA not realizing they misread. It states a maximization and hands you positions and a count. It looks like a job for a clever greedy or a DP over the array. Instead you binary search on the answer itself, and the whole problem collapses into a linear feasibility check. Miss that reduction and you burn the per-question timer building a table that never converges. The other three are more honest about what they are. Each still hides a detail the interviewer watches for. For the trading DP it is the rolling four-variable trick. On inversions it is the merge step that does the counting at no extra cost, and on bridges the reciprocal bookkeeping that separates a bridge from an ordinary edge.

What's inside

4 problems, worked step by step
about 40 min

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What candidates walked out with, from 20,000+ reports, forum threads behind logins and write-ups in Chinese. Then solved step by step.

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The Core Coding Round

These took digging.

Know what D. E. Shaw asks before you walk in.