Hashing Questions Long
Linear probing is a collision resolution technique used in hashing to handle collisions that occur when two or more keys are mapped to the same hash index. It is a simple and commonly used method to resolve collisions in open addressing schemes.
In linear probing, when a collision occurs, the algorithm searches for the next available slot in the hash table by incrementing the index linearly until an empty slot is found. The probing sequence follows a linear progression, hence the name "linear probing."
To illustrate the process, let's assume we have a hash table with a fixed size of N slots. When a key is hashed and a collision occurs at index i, the algorithm checks the next slot (i+1). If it is empty, the key is inserted there. If not, it continues to check the subsequent slots until an empty slot is found.
If the end of the hash table is reached, the algorithm wraps around to the beginning and continues the search until an empty slot is found or the entire table has been traversed. This wrap-around behavior ensures that all slots in the hash table are probed.
When searching for a key, the linear probing technique follows a similar process. It starts at the hashed index and checks if the key is present. If not, it continues to search the subsequent slots until the key is found or an empty slot is encountered.
However, one drawback of linear probing is the clustering effect. As keys are inserted and collisions occur, consecutive keys tend to cluster together, forming long runs of filled slots. This clustering can lead to increased search times and decreased performance.
To mitigate this issue, various techniques can be employed, such as double hashing or quadratic probing, which provide alternative ways to determine the next slot to probe. These techniques aim to distribute the keys more evenly throughout the hash table, reducing clustering and improving performance.
In summary, linear probing is a collision resolution technique in hashing that handles collisions by linearly searching for the next available slot in the hash table. While it is simple to implement, it can suffer from clustering, which can impact performance.