Summary

Use perfect_hashing for a static_set of keys. It creates a collision_free mapping from keys to table slots. Lookups are O_1_lookup after you build the structure. Many implementations use two_level_hashing with a universal_hash_family to place keys. A minimal_perfect_hash uses exactly n slots for n keys. Expect extra preprocessing_time to construct the tables. Watch space_complexity during the build. Queries are constant time and deterministic for the fixed set.