Perfect hashing

A perfect hash function allows the storage of a set of records in a minimum amount of memory, like in a table of the size equal to the number of keys times the key size, is called minimal perfect hash function. Minimal perfect hash functions are used for memory efficient storage and fast retrieval of items from static sets. The basic definitions and finding the perfect and minimal perfect hash functions by trial and error are presented. The difficulties which are encountered in designing such a function and the space and time requirements for perfect hash functions are also discussed.