Why Hash Is Used in Data Structure?


Angela Bailey

Hash is a fundamental concept in data structures, and it plays a crucial role in various algorithms and applications. In this article, we will explore why hash is used and its significance in data structure.

What is Hash?

Hashing is a technique used to map data to a fixed-size array, known as a hash table or hash map. It involves converting an input into a numerical value called a hash code or hash value. The hash code is then used as an index to store and retrieve the data quickly.

Why Use Hash?

The primary reason for using hashing in data structures is efficiency. Hashing allows for constant-time average-case performance for common operations like insertion, deletion, and search.

1. Fast Retrieval

A key advantage of using hashing is its ability to provide fast retrieval of data. Instead of searching through an entire collection sequentially, the hash code allows direct access to the desired element’s location in the hash table.

2. Collision Resolution

In some cases, two different inputs might produce the same hash code, known as a collision. To handle collisions efficiently, various collision resolution techniques are employed.

  • Chaining: In chaining, each index of the hash table stores a linked list of elements that hashed to that index. When collisions occur, new elements are appended to the linked list at the corresponding index.
  • Open Addressing: Open addressing involves storing colliding elements in alternative locations within the same table by using probing techniques like linear probing or quadratic probing.

3. Efficiency Trade-Off

The choice of a suitable hashing algorithm depends on the specific requirements of an application.

While hashing provides fast retrieval, it comes with a trade-off in terms of memory usage. A larger hash table may be required to reduce collisions and maintain acceptable performance.

Common Applications of Hashing

Hashing is widely used in various applications, including:

  • Password Storage: Hash functions are commonly used to store passwords securely. Instead of storing the actual password, a hash value is stored.

    During authentication, the user’s input is hashed and compared with the stored hash for verification.

  • Data Integrity: Hash functions are used to ensure data integrity by producing a unique hash value for a given set of data. Any changes in the data will result in a different hash value, indicating that the data has been tampered with.
  • Indexing and Searching: Hashing allows for efficient indexing and searching in databases. It enables quick lookup of records based on key values without scanning the entire database.


Hashing is a fundamental concept in data structures that provides efficient storage and retrieval of data. It enables fast access to elements through direct indexing, resolves collisions using various techniques, and finds applications in areas like password storage, data integrity verification, and database indexing.

In summary, understanding why hash is used and its significance can greatly enhance your knowledge of data structures and algorithms.

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