Question 16861 – Hashing

An algorithm has to store several keys generated by an adversary in a hash table. The adversary is malicious who tries to maximize the number of collisions. Let k be the number of keys, m be the number of slots in the hash table, and k>m. Which one of the following is the best hashing strategy to counteract the adversary?

Correct Answer: C

Division method, i.e., use the hash function h(k) = k mod m.

Multiplication method, i.e., use the hash function h(k) = ⌊m(kA − ⌊kA⌋)⌋, where A is a carefully chosen constant.

Universal hashing method.

If k is a prime number, use Division method. Otherwise, use Multiplication method.