Technical Screen

A Stream-Transformer Coding Question from the Phone Screen

Jane StreetSoftware Engineer · New Grad · Technical Screen · Feb 2026

This is an old one — sharing a question from my campus recruiting interview back in the day. Given a set of M codes and N timestamps, the ideal shape for the data is an N x M matrix, where the rows are sorted by time and the columns are sorted by the code's lexicographic order. But not every code has data at every timestamp. You're given a stream of std::vector >,…

Shared by a candidate · reported Feb 2026. Interview formats change; use it as a guide, not a script.