Arrays Linked Lists Questions Long
A hash table is a data structure that allows efficient storage and retrieval of key-value pairs. It is also known as a hash map or associative array. The main idea behind a hash table is to use a hash function to map keys to an index in an array, called a hash table or hash array. This index is used to store the corresponding value.
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 hash table where the key-value pair will be stored. The hash function should ideally distribute the keys uniformly across the hash table to minimize collisions, which occur when two or more keys map to the same index.
In the case of implementing a hash table using linked lists, each index in the hash table array contains a linked list. When a key-value pair needs to be inserted, the hash function is applied to the key to determine the index. If there is no linked list at that index, a new linked list is created, and the key-value pair is inserted as the first node in the list. If a linked list already exists at that index, the key-value pair is appended to the end of the list.
To retrieve a value based on a key, the hash function is applied to the key to determine the index. Then, the linked list at that index is traversed to find the node with the matching key. If the key is found, the corresponding value is returned. If the key is not found, it means that the key-value pair does not exist in the hash table.
The advantage of using linked lists in the implementation of a hash table is that it allows handling collisions efficiently. Collisions occur when two or more keys map to the same index. In such cases, the linked list at that index can be used to store multiple key-value pairs. This ensures that all key-value pairs are stored and can be retrieved correctly.
However, it is important to note that the efficiency of a hash table depends on the quality of the hash function and the distribution of keys. A good hash function should minimize collisions and distribute the keys uniformly across the hash table. If the hash function is poorly designed or if there are too many collisions, the performance of the hash table can degrade, resulting in slower insertion and retrieval operations.
In summary, a hash table is a data structure that uses a hash function to map keys to an index in an array. When implementing a hash table using linked lists, each index in the array contains a linked list to handle collisions. This allows efficient storage and retrieval of key-value pairs, ensuring that all pairs are stored correctly and can be accessed in constant time on average.