A hash table is a data structure that stores a set of items, each of which maps a specific key to a specific value. There are many ways to implement a hash table, but they all have one thing in common: buckets. Every hash table maintains an array of buckets somewhere, and each item belongs to exactly one bucket.
To determine the bucket for a given item, you typically hash the item’s key, then compute its modulus – that is, the remainder when divided by the number of buckets. For a hash table with 16 buckets, the modulus is given by the final hexadecimal digit of the hash.
Inevitably, several items will end up belonging to same bucket. For simplicity, let’s suppose the hash function is invertible, so that we only need to store hashed keys. A well-known strategy is to store the bucket contents in a linked list: