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Jane Street hires through practical, conversational interviews rather than puzzle-bank recall. Engineering rounds are small, realistic programming tasks written without running code and judged on clarity and correctness, while trading and research loops rely on interactive games, live market making and probability reasoning under persistent questioning.

Coding problems
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Connect-N on an Unbounded Board

Implement Connect-N on a board unbounded both horizontally (any integer column, including negatives) and vertically: insert(col, player) places a piece and reports whether a player now has N consecutive pieces along a row or a column. The hard part is the row check across columns of uneven height; the key hint is to inspect only the rows and column touched by the latest insert. A push-from-bottom variant shifts the whole column up on each insert, so several rows change at once and both players can win on the same move.

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data-structure
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