Hash Function in Data Structure - GATE CSE Notes (2024)

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What is hashing function in data structure notes? ›

Hashing works by converting the key into an index that is used to access the data. Hash functions are used to create hash tables. Hash tables are data structures that store data in an array using a hash function to map keys to values. Hash tables are used to store data in a way that is efficient and easy to search.

A hash function is a deterministic function that maps a set of strings or keys to a set of bounded integers. It can also include objects, data structures, or anything that can be represented unambiguously as a string.

In data structure, hashing helps in narrowing down search and find number within seconds. Hashing is the process of converting input data of any size into a fixed-size value, usually for the purpose of fast data retrieval.

Hash Function is used to index the original value or key and then used later each time the data associated with the value or key is to be retrieved. Thus, hashing is always a one-way operation. There is no need to "reverse engineer" the hash function by analyzing the hashed values.

With modular hashing, the hash function is simply h(k) = k mod m for some m (usually, the number of buckets). The value k is an integer hash code generated from the key. If m is a power of two (i.e., m=2^p), then h(k) is just the p lowest-order bits of k.

Say we are given keys in the range 0 to 999, and have a hash table of size 10. In this case, a possible hash function might simply divide the key value by 100. Thus, all keys in the range 0 to 99 would hash to slot 0, keys 100 to 199 would hash to slot 1, and so on.

Common hash functions include: Division Method: Key % Hash Table Size. Multiplication Method: (Key * Constant) % Hash Table Size. Universal Hashing: A family of hash functions designed to minimize collisions.

The multiplication method for creating hash functions operates in two steps. First, we multiply the key k by a constant A in the range 0< A < 1 and extract the fractional part of kA. Then, we multiply this value by m and take the floor of the result.

The schemes of hashing used in integer universe assumption include hashing by division, hashing by multiplication, universal hashing, dynamic perfect hashing, and static perfect hashing. However, hashing by division is the commonly used scheme.

The most common hash functions used in digital forensics are Message Digest 5 (MD5), and Secure Hashing Algorithm (SHA) 1 and 2.

Why is hash function used? ›

Hashing is commonly used to ensure data integrity. By generating a hash value for an amount of data, such as a file or message, a user can later compare it with the hash value of the received data to verify if any changes or corruption occurred during transmission. Efficient data retrieval.

Hashing is a one-way mathematical function that turns data into a string of nondescript text that cannot be reversed or decoded. In the context of cybersecurity, hashing is a way to keep sensitive information and data — including passwords, messages, and documents — secure.

Hashing is the process of indexing and retrieving data items in a data structure to provide faster way (preferably O(1)) of finding the element using the hash function. Note: The hashed values are kept in a data structure known as hash tables.

Hash tables are a type of data structure in which the address/ index value of the data element is generated from a hash function. This enables very fast data access as the index value behaves as a key for the data value.