Hash tables - C Programming.

Hash tables are a powerful and versatile data structure used in computer science to store and retrieve data quickly and efficiently.

In C programming, they are frequently used for a variety of tasks, such as symbol tables, database indexing, and caching. Hash tables may be unfamiliar to you, so you may be asking what they are, how they operate, and why they are significant. The major features and implementation of hash tables in C programming will be covered in this article. This article will provide you with a thorough grasp of hash tables and how to utilize them efficiently in your projects, whether you're a novice or a seasoned programmer. Let's get started and discover the potential of hash tables in C programming!

To comprehend hash tables, imagine a large library filled with books. An ISBN is a special identification number that is assigned to every book. The system is used by library personnel to swiftly and effectively store and retrieve books. Each book is given a specific spot on the shelf and is arranged according to its ISBN in a catalog. So a hash table can be compared to a catalog system in a library.

A hash table is a type of data structure that makes key-value pairs easily searchable, addable, and removable. It employs a hash function to translate keys into array indices, where each index denotes a bucket that holds a linked list of key-value pairs. The key-value pair should be saved at the appropriate index in the array, which is determined by the hash function, which accepts a key as input and returns an integer value.

Here are the main components of the hash table:

1. Hash function: A hash function is a mathematical function that takes a key and returns an index in the array where the value is stored. The hash function should be designed to minimize collisions, where two different keys generate the same index. A good hash function will distribute the keys evenly across the array, reducing the likelihood of collisions and improving the performance of the hash table.

2. Array: An array is a data structure that stores elements in contiguous memory locations. In a hash table, the array is used to store the values associated with the keys. The size of the array is determined by the expected number of key-value pairs and the desired load factor, which is the ratio of the number of elements in the array to the size of the array.

3. Buckets: Each index in the array is called a bucket, and it contains a linked list of nodes that store the key-value pairs. When a new key-value pair is added to the hash table, the hash function is used to determine the index in the array where the value should be stored. If there is already a value stored at that index, a new node is added to the linked list.

4. Nodes: A node is a data structure that stores a key-value pair and a pointer to the next node in the linked list. When a new key-value pair is added to the hash table, a new node is created and added to the linked list at the corresponding index in the array.

/* Hash table structure */
typedef struct table {
    node_t** buckets;
    int size;
} table_t;

/* Hash node structure */
typedef struct node {
    char* key;
    char* value;
    struct node* next;
} node_t;

/* Define the HashTable item */

typedef struct Ht_item

{

char* key;

char* value;

} Ht_item;

Here's how Hash Function works:

1. Initialize a variable hash to 0.

2. Calculate the length of the string key.

3. Loop through each character in the string key and add its ASCII value to the hash variable.

4. Return the remainder of hash when divided by TABLE_SIZE, which ensures that the index is within the bounds of the hash table array.

HAPPY CODING!