Robinhood·Software Engineer·Technical Phone Screen
May 2026
Robinhood software engineer screen, one question, very technical and specific. They wanted working code plus correctness under edge cases, and the O(1) space constraint was the part that tripped me up most.
- Write a function that parses a string of OHLC candlestick records (semicolon-separated, comma-separated fields) and returns a classification string where each character is 'B' (bullish), 'S' (bearish), 'D' (doji), or 'X' (invalid record). Constraints: up to 200k records, single-pass O(total input length) time, O(1) extra space beyond the output, no converting the input to arrays.
“The classification logic itself is fine, close vs open comparison is trivial.” The rest of the author's notes on Software Engineer interview at Robinhood, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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