Hashing Questions Medium
A hash table is a data structure that stores key-value pairs, where each key is unique. It uses a hash function to map the keys to an index in an array, which is called the hash table. The hash function takes the key as input and computes a hash code, which is an integer value. This hash code is then used to determine the index in the array where the key-value pair will be stored.
To implement a hash table, the following steps are typically followed:
1. Create an array of a fixed size to serve as the hash table.
2. Define a hash function that takes a key as input and returns a hash code.
3. Use the hash code to determine the index in the array where the key-value pair will be stored.
4. If there is a collision, i.e., two keys produce the same hash code, handle it using a collision resolution technique. Some common techniques include chaining (using linked lists to store multiple values at the same index) or open addressing (finding an alternative index to store the value).
5. Store the key-value pair at the determined index in the hash table.
6. To retrieve a value, provide the key to the hash function, compute the hash code, and use it to find the index in the array. If there is a collision, use the collision resolution technique to find the correct value.
7. To delete a value, locate the key in the hash table using the same steps as retrieval and remove the key-value pair from the table.
Overall, a hash table provides efficient insertion, retrieval, and deletion operations, as the time complexity for these operations is typically O(1) on average. However, the performance can degrade if there are many collisions or if the hash function is not well-distributed.