What Is Mean by **Hashing** in Data Structure?

In computer science, **hashing** is a technique used to map data of any size to a fixed-size value. This fixed-size value is typically an integer and is called the __hash value__, __hash code__, or simply the __hash__. The process of converting data into this fixed-size value is known as __hash function__.

## Why Use Hashing?

**Hashing** provides a way to efficiently store and retrieve data. It is commonly used in various applications such as:

**Databases:**Hashing allows for quick lookup, insertion, and deletion of data records.**Cryptographic systems:**Hash functions are utilized to ensure data integrity and security.**Caching mechanisms:**Hash tables are employed to cache frequently accessed data for faster retrieval.**Data compression algorithms:**Hash functions help reduce the size of large datasets.

## The Process of Hashing

The process of hashing involves the following steps:

__Data input:__A piece of data, such as a string or an object, is provided.__Hash function application:__The hash function takes the input and produces a hash value.__Data storage/retrieval:__The hash value is used as an index or key to store or retrieve the corresponding data in a hash table or similar structure.

### The Role of Hash Functions

A __hash function__ is responsible for transforming data into a fixed-size value. It should:

- Be deterministic: For the same input, it should always produce the same hash value.
- Have a fixed output size: The hash value should have a consistent length regardless of the input size.
- Generate unique hash values: Ideally, each unique input should result in a unique hash value.
- Produce evenly distributed hash values: The hash function should distribute the hash values uniformly across the range of possible values.
- Have efficient computation: The hash function should be computationally inexpensive to calculate.

### Collision Resolution

In some cases, two different inputs may produce the same hash value. This is known as a __collision__. Collision resolution techniques are employed to handle such situations and ensure data integrity and correct retrieval.

**Open addressing** and **chaining** are two commonly used collision resolution techniques. Open addressing involves finding an alternative empty slot when a collision occurs, while chaining uses linked lists to store multiple elements with the same hash value.

## In Conclusion

**Hashing** is a powerful technique used in various domains to efficiently store and retrieve data. It allows for quick access to information by utilizing a fixed-size representation of data through a hash function. Understanding how hashing works and the importance of choosing an appropriate hash function is crucial for designing effective data structures and algorithms.