Hashing Questions Medium
A hash table and a hash map are both data structures that use the concept of hashing to store and retrieve data efficiently. However, there is a subtle difference between the two.
A hash table is a data structure that uses an array to store key-value pairs. It uses a hash function to convert the key into an index of the array, where the corresponding value is stored. The hash function ensures that each key is mapped to a unique index, allowing for constant-time average case complexity for insertion, deletion, and retrieval operations. In a hash table, the keys are not ordered.
On the other hand, a hash map is an implementation of a hash table that allows null values and only one null key. It is typically implemented as a combination of a hash table and a linked list. In addition to the benefits of a hash table, a hash map also maintains the order of insertion of key-value pairs, allowing for iteration in the order of insertion. This makes a hash map suitable for scenarios where the order of elements is important.
In summary, the main difference between a hash table and a hash map lies in the ordering of key-value pairs. A hash table does not maintain any specific order, while a hash map preserves the order of insertion.