What is a hash table?

A hash table, also known as a hash map, is a data structure that allows efficient storage and retrieval of key-value pairs. It uses a technique called hashing to map keys to specific positions in an array, known as buckets or slots. The hash function takes the key as input and computes a hash code, which is used to determine the index of the bucket where the corresponding value will be stored.

The main advantage of a hash table is its ability to provide constant-time average case complexity for insertion, deletion, and retrieval operations. This is achieved by minimizing the number of collisions, which occur when two different keys are mapped to the same bucket. To handle collisions, various collision resolution techniques can be employed, such as chaining (using linked lists to store multiple values in the same bucket) or open addressing (probing other buckets to find an empty slot).

Hash tables are widely used in computer science and are particularly useful when there is a need for fast access to data based on a unique key. They are commonly used in applications like databases, caches, symbol tables, and language interpreters. However, it's important to note that the performance of a hash table depends on the quality of the hash function and the load factor (ratio of stored elements to the total number of buckets), which can affect the number of collisions and overall efficiency.