Explain the role of collision handling in hash tables.

Collision handling in hash tables is used to resolve conflicts that occur when two keys hash to the same index.

In a hash table, data is stored in an array format, where each data value has its own unique index value. The index value is calculated using a hash function. However, there can be instances where two different keys produce the same hash, leading to a collision. This is where collision handling comes into play.

There are several methods of collision handling, each with its own advantages and disadvantages. The simplest method is called 'separate chaining'. In this method, each cell in the hash table points to a linked list of records that have the same hash. When a collision occurs, the new key is simply added to the end of the list. This method is simple and effective, but it can lead to long linked lists, which can slow down search times.

Another method is 'open addressing', where all elements are stored in the hash table itself. When a collision occurs, the hash table looks for the next available slot and stores the key there. This method is more space-efficient than separate chaining, but it can lead to clustering, where a group of adjacent cells become filled, slowing down the search time.

A more complex method is 'double hashing', which uses a second hash function to calculate a new index when a collision occurs. This method can avoid the problem of clustering, but it requires more computational power.

In conclusion, collision handling is a crucial aspect of hash tables. It ensures that every key has a unique index in the hash table, preventing data loss and ensuring efficient data retrieval. Without effective collision handling, the performance of a hash table can be significantly reduced.