Coding problems using hashing (2024)

FAQs

How to solve problems using hashing? ›

Now when we want to search for an item, we simply use the hash function to compute the slot name for the item and then check the hash table to see if it is present. This searching operation is , since a constant amount of time is required to compute the hash value and then index the hash table at that location.

In the worst case scenario, all the keys hash to the same index. The performance of a hash table look up degrades from O(1) constant time to O(n) linear time. The hash table performs no better than a linear search in an array.

Hashing is designed to solve the problem of needing to efficiently find or store an item in a collection. For example, if we have a list of 10,000 words of English and we want to check if a given word is in the list, it would be inefficient to successively compare the word with all 10,000 items until we find a match.

Instead of maintaining a dictionary, a feature vectorizer that uses the hashing trick can build a vector of a pre-defined length by applying a hash function h to the features (e.g., words), then using the hash values directly as feature indices and updating the resulting vector at those indices.

Password hashing is a means of protecting users' passwords from getting into the hands of hackers. However, password hashing isn't risk-free. In this method, passwords are transformed into a predictable and consistent pattern which can be attacked using dictionary, brute-force, or rainbow table attacks.

There are many practical examples of hash tables used in every-day life. A popular example is in username-password databases. Every time someone signs up on a website using a username and password, that information must be stored somewhere for later retrieval.

Search algorithms: Hashing is used to implement search algorithms, such as hash tables and bloom filters, for fast lookups and queries. Cryptography: Hashing is used in cryptography to generate digital signatures, message authentication codes (MACs), and key derivation functions.

A list is typically ordered whereas a hashtable is not. So when you add elements into a list and expect the ordering to remain consistent then an array retains the ordering while a hashtable gives no guarantee as to the order you get back out. That's why we use an array to implement a list instead of a hash table.

Is a hash table better than arrays? ›

In summary, arrays are great for situations where you have a fixed sequence of elements and need fast index-based access, while hash tables are better when you have key-value pairs and need efficient lookups, insertions, and deletions based on keys.

For example, if the input is 123,456,789 and the hash table size 10,000, squaring the key produces 15,241,578,750,190,521, so the hash code is taken as the middle 4 digits of the 17-digit number (ignoring the high digit) 8750.

A hash cannot be reversed back to the original data because it is a one-way operation. Hashing is commonly used to verify the integrity of data, commonly referred to as a checksum. If two pieces of identical data are hashed using the same hash function, the resulting hash will be identical.

SHA-256 it's a NIST's (National Institute of Standards and Technology) recommended and officially approved standard algorithm. Thanks to the possibility of verifying the content of data without showing it, it's also used by many governments and public-sector agencies worldwide, including the U.S. and Australia.

Hashing is implemented in two steps: An element is converted into an integer by using a hash function. This element can be used as an index to store the original element, which falls into the hash table. The element is stored in the hash table where it can be quickly retrieved using hashed key.

This method involves dividing the key by the table size and taking the remainder as the hash value. For example, if the table size is 10 and the key is 23, the hash value would be 3 (23 % 10 = 3).

One, hashing is a one-way function. It can be used on any input data to generate a hash value. But, applying a hash function to a hash value will not reveal the input data. Second, hashing always produces a fixed-length hash value, irrespective of the length/ size of the input.