Hashing Questions Medium
In hashing, a hash collision occurs when two different inputs produce the same hash value. This can happen due to the limited range of hash values compared to the potentially infinite number of inputs.
To handle hash collisions, various techniques are employed:
1. Separate Chaining: In this approach, each hash table slot contains a linked list or any other data structure to store multiple values with the same hash value. When a collision occurs, the new value is simply appended to the existing list at the corresponding slot.
2. Open Addressing: In this method, when a collision occurs, the algorithm searches for the next available slot in the hash table to store the value. There are different techniques within open addressing, such as linear probing (checking the next slot), quadratic probing (checking slots with quadratic increments), and double hashing (using a second hash function to determine the next slot).
3. Robin Hood Hashing: This technique aims to minimize the variance in the lengths of the linked lists in separate chaining. When a collision occurs, it checks the difference in the lengths of the two colliding slots. If the new value has a shorter distance to its ideal slot, it displaces the existing value and continues to move the displaced value until it finds a slot with a shorter distance.
4. Cuckoo Hashing: This method uses multiple hash functions and multiple hash tables. When a collision occurs, it checks the alternate hash table and swaps the values if necessary. This process continues until a vacant slot is found or a maximum number of swaps is reached.
Overall, the goal of handling hash collisions is to ensure efficient storage and retrieval of data while minimizing the chances of collisions and maintaining a balanced distribution of values across the hash table.