A hash table collision happens when two different keys produce the same hash value and, therefore, map to the same index in a hash table. A hash table is a data structure that uses a hash function to compute an index (or hash code) into an array of buckets or slots, from which the desired value can be found. The purpose of using a hash table is to allow for fast data retrieval.
When a collision occurs, the hash table must handle it to maintain the integrity of the data structure. There are several strategies for collision resolution:
- Chaining: In this method, each slot in the hash table contains a linked list of all entries that hash to the same index. When a collision occurs, the new entry is simply added to the list.
- Open Addressing: This technique searches for the next available slot in the array when a collision occurs. Methods like linear probing, quadratic probing, or double hashing are used to find an open index.
Collisions are a natural occurrence in hash tables, especially when the number of keys exceeds the number of available slots. To minimize collisions, a good hash function should distribute keys uniformly across the hash table. Additionally, resizing the hash table (rehashing) can help reduce the likelihood of collisions by increasing the number of available slots.
In summary, managing hash table collisions is crucial for maintaining efficient data retrieval and ensuring that the hash table performs optimally.