Hash Table
External
Internal
Overview
Hash tables are one of the most used data structures in programming. They don't have that many operations (INSERT(), DELETE() and SEARCH()), but what they do, they do really well. Conceptually, a hash table is an array that provides immediate random access for constant time insertion, deletion and lookup based on an arbitrary key and not an integral index, for a dynamic set of keys. The hash map implementation do store data in proper arrays, and the mapping between the arbitrary key and the integral position in the array is provided by a hash function.
Canonical Use
Hash tables are used in situations where we need to do fast lookups of arbitrary keys.
Hash Table Implementation Discussion
The purpose of a hash table is to maintain a dynamic set of records, each record identified by a unique key, and provide constant time insertion, deletion and search.
Chaining
Linear Probing
Hash Functions
Supported Operations
INSERT(X)
Add a new key/value pair INSERT(X) to the hash map in O(1) running time.