Hash Table
I. What is Hash Table?
Hash table: A data structure for keeping keys and values together. The right value is obtained by computing an index into an array of buckets or slots using a hash function.
The basic idea is to use a hash function that takes in a key and returns an index in the array. The key is then stored at this index, so that it can be quickly retrieved later. To retrieve a value, the hash function is used again to find the index at which the key is stored, and the value is returned.
Hash tables are very efficient for searching, inserting, and deleting data, with an average time complexity of O (1). However, they can become inefficient if the hash function is not well-designed, or if the hash table becomes too full, in which case the time complexity can degrade to O(n).
II. Importance of Hash table?
Hash table are an important data structure because they allow efficient access to data using keys. These include databases, caches, and associative arrays in computer languages, all of which need quick lookup.
Hash tables’ consistent time complexity for finding, insertion, and deletion of data is one of its key benefits. This indicates that, on average, the time required to complete these operations is independent of the size of the data collection. Hash tables are therefore ideal for huge data sets when quick data access is essential.
III. Hash table operations?
The main operations of a hash table are:
l) Insertion: The hash function is used to map the key to a position in the array in order to add a new key-value pair to the hash table. The key-value pair can be placed straight in the slot if it is empty. A collision has occurred and the key-value pair has to be put elsewhere in the database if the slot is already taken. There are several methods for managing collisions, such as open addressing or chaining (which stores the key-value pair in a linked list at the collision slot) (finding an empty slot in the array to store the key-value pair).
2) Lookup: The hash function is used to map a key to a slot in the array so that the value associated with it can be retrieved. The value of the key is returned if it is discovered in the slot. If the key cannot be located, the table lacks the key, and the lookup operation is unsuccessful.
3)Deletion: The hash function is used to map the key to a position in the array in order to delete a key-value pair from the hash table. It is taken off the table if the key is discovered in the slot. If the key cannot be located, the remove action is unsuccessful because the table does not include the key.
IV. Variations Hash table?
Using an array with a hash function is one method of creating a hash table. The values are kept at the indices where the hash function converts the keys to integers in the array.
There are many variations of hash tables, such as
l) Separate cleaning: Each member of the array in separate chaining is a linked list, and if a collision happens (two keys hash to the same index), the new key-value pair is appended to the linked list at that index.
2) Open addressing: When a collision occurs in open addressing, the hash table searches for the following vacant space in the array to store the new key-value pair. There are numerous methods for deciding which slot to pick, including double hashing, linear probing, and quadratic probing.
3) linear probing: is a straightforward open addressing approach where the hash table checks each slot in the array sequentially, beginning at the index where the collision happened, to find the next empty slot.
V. Implementation Hash table?
There are several ways to implement a hash table, but one common approach is to use an array as the underlying data structure and a hash function that maps keys to indices in the array. The array is called the “bucket array” and each element in the array is called a “bucket”.
VI. Application Hash table?
Hash tables are used in a wide variety of applications, including:
1) Database indexing.
2) Caches.
3) Full-text search.
4)Network communication.
5) Data compression.
6) Programming language implementation
VII. Other Interesting aspects of Hash table?
l There are several ways to build hash tables, including utilizing an array, a linked list, or a binary tree. The performance of the hash table may be impacted by the implementation choice.
l) Sets, maps, and multi-maps are just a few of the numerous data structures that may be implemented using hash tables.
2) A distributed cache may be implemented using hash tables, where the data is kept on several servers and the keys are hashed to decide which server it should be on.
VIII. Simple Hash Table code?
