table de hachage en c
Explanation of Hash Tables in C
A hash table, also known as a hash map, is a data structure that allows for efficient insertion, deletion, and retrieval of key-value pairs. It is implemented using an array and a hash function. Here is an explanation of each step involved in implementing a hash table in C:
Hash Function: A hash function takes a key as input and returns an index in the array where the corresponding value will be stored. The goal of a good hash function is to distribute the keys uniformly across the array to minimize collisions. Collisions occur when two different keys produce the same hash value.
Array: The hash table is implemented using an array of fixed size. Each element in the array is called a bucket or a slot. The size of the array determines the number of possible hash values and, therefore, the number of keys that can be stored in the hash table.
Insertion: To insert a key-value pair into the hash table, the hash function is applied to the key to determine the index in the array where the value will be stored. If there is no collision (i.e., the bucket is empty), the value is stored in the corresponding bucket. If there is a collision, different collision resolution techniques can be used, such as chaining or open addressing.
Chaining: Chaining is a collision resolution technique where each bucket in the array is implemented as a linked list. If a collision occurs, the new key-value pair is appended to the linked list at the corresponding bucket index.
Open Addressing: Open addressing is another collision resolution technique where, if a collision occurs, the algorithm probes for the next available bucket in a predetermined sequence until an empty bucket is found. Common probing methods include linear probing, quadratic probing, and double hashing.
Retrieval: To retrieve the value associated with a given key, the hash function is applied to the key to determine the index in the array. If there is no collision, the value is retrieved from the corresponding bucket. If there is a collision, the linked list (in the case of chaining) or the probing sequence (in the case of open addressing) is traversed until the key is found.
Deletion: To delete a key-value pair from the hash table, the hash function is applied to the key to determine the index in the array. If there is no collision, the value is removed from the corresponding bucket. If there is a collision, the linked list (in the case of chaining) or the probing sequence (in the case of open addressing) is traversed until the key is found and then removed.
It is important to note that the efficiency of a hash table depends on the quality of the hash function, the size of the array, and the chosen collision resolution technique. A well-designed hash function and an appropriately sized array can minimize collisions and provide efficient operations.