Find duplicate files in a directory tree by content: size prefilter, then hashing.

A grounded systems-coding screen: find files with identical content across a tree. The naive all-pairs hash is wasteful. The signal is the size prefilter and a cheap-hash gate before the full hash. Here is the layered approach.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.