What is Rehashing?

What is Hashing?

Hashing in Data Structures refers to the process of transforming a given key to another value. It involves mapping data to a specific index in a hash table using a hash function that enables fast retrieval of information based on its key. The transformation of a key to the corresponding value is done using a Hash Function and the value obtained from the hash function is called Hash Code ....

Need for Hash data structure

Every day, the data on the internet is increasing multifold and it is always a struggle to store this data efficiently. In day-to-day programming, this amount of data might not be that big, but still, it needs to be stored, accessed, and processed easily and efficiently. A very common data structure that is used for such a purpose is the Array data structure....

Components of Hashing

There are majorly three components of hashing:...

How does Hashing work?

Suppose we have a set of strings {“ab”, “cd”, “efg”} and we would like to store it in a table....

What is a Hash function?

The hash function creates a mapping between key and value, this is done through the use of mathematical formulas known as hash functions. The result of the hash function is referred to as a hash value or hash. The hash value is a representation of the original string of characters but usually smaller than the original....

Problem with Hashing

If we consider the above example, the hash function we used is the sum of the letters, but if we examined the hash function closely then the problem can be easily visualized that for different strings same hash value is begin generated by the hash function....

What is Collision?

Collision in Hashing occurs when two different keys map to the same hash value. Hash collisions can be intentionally created for many hash algorithms. The probability of a hash collision depends on the size of the algorithm, the distribution of hash values and the efficiency of Hash function....

How to handle Collisions?

There are mainly two methods to handle collision:...

What is meant by Load Factor in Hashing?

The load factor of the hash table can be defined as the number of items the hash table contains divided by the size of the hash table. Load factor is the decisive parameter that is used when we want to rehash the previous hash function or want to add more elements to the existing hash table....

What is Rehashing?

As the name suggests, rehashing means hashing again. Basically, when the load factor increases to more than its predefined value (the default value of the load factor is 0.75), the complexity increases. So to overcome this, the size of the array is increased (doubled) and all the values are hashed again and stored in the new double-sized array to maintain a low load factor and low complexity....

Applications of Hash Data structure

Hash is used in databases for indexing. Hash is used in disk-based data structures. In some programming languages like Python, JavaScript hash is used to implement objects....

Real-Time Applications of Hash Data structure

Hash is used for cache mapping for fast access to the data. Hash can be used for password verification. Hash is used in cryptography as a message digest. Rabin-Karp algorithm for pattern matching in a string. Calculating the number of different substrings of a string....

Advantages of Hash Data structure

Hash provides better synchronization than other data structures. Hash tables are more efficient than search trees or other data structures Hash provides constant time for searching, insertion, and deletion operations on average....

Disadvantages of Hash Data structure

Hash is inefficient when there are many collisions. Hash collisions are practically not avoided for a large set of possible keys. Hash does not allow null values....

Frequently Asked Questions(FAQs) on Hashing:

1. What is a Hash function?...

Conclusion

From the above discussion, we conclude that the goal of hashing is to resolve the challenge of finding an item quickly in a collection. For example, if we have a list of millions of English words and we wish to find a particular term then we would use hashing to locate and find it more efficiently. It would be inefficient to check each item on the millions of lists until we find a match. Hashing reduces search time by restricting the search to a smaller set of words at the beginning....