C Program To Implement Dictionary Using Hashing Algorithms

To implement a robust dictionary in C using hashing, you should focus on three core components: a reliable hash function collision resolution strategy dynamic resizing to maintain performance. 1. Robust Hash Function (FNV-1a) For strings, the FNV-1a algorithm

Inserts at the head of the chain. Cost comes from collision checking.

An array of structs, where each struct holds the word (key) and its definition (value).

Ideally, two different keys would never map to the same index. In reality, because the set of possible keys is usually larger than the size of the array, collisions are inevitable.

while ((c = key++)) hash_val = ((hash_val << 5) + hash_val) + c; / hash_val * 33 + c */ c program to implement dictionary using hashing algorithms

Hashing transforms a "key" (like a word) into an integer index. This index tells us exactly where to store the corresponding "value" (the definition) in an array. Takes a string and returns an integer.

A mechanism to handle situations where two different keys produce the same hash index. Because the array size is finite and the number of possible keys is infinite, collisions are inevitable. 2. Choosing a Collision Resolution Strategy

#include #include #include #define TABLE_SIZE 10 typedef struct Node char* key; char* value; struct Node* next; Node; typedef struct Node* buckets[TABLE_SIZE]; Dictionary; // Initialize all bucket pointers to NULL void init_dictionary(Dictionary* dict) for (int i = 0; i < TABLE_SIZE; i++) dict->buckets[i] = NULL; // DJB2 Hashing Algorithm unsigned int hash_function(const char* key) unsigned long int hash = 5381; int c; while ((c = *key++)) hash = ((hash << 5) + hash) + c; return hash % TABLE_SIZE; // Create a new key-value node Node* create_node(const char* key, const char* value) Node* new_node = (Node*)malloc(sizeof(Node)); if (!new_node) perror("Memory allocation failed"); exit(EXIT_FAILURE); new_node->key = strdup(key); new_node->value = strdup(value); new_node->next = NULL; return new_node; // Insert or Update a key-value pair void insert(Dictionary* dict, const char* key, const char* value) unsigned int index = hash_function(key); Node* head = dict->buckets[index]; Node* temp = head; // Check if the key already exists to update its value while (temp != NULL) if (strcmp(temp->key, key) == 0) free(temp->value); temp->value = strdup(value); return; temp = temp->next; // Key does not exist, insert a new node at the front of the chain Node* new_node = create_node(key, value); new_node->next = dict->buckets[index]; dict->buckets[index] = new_node; // Search for a value by its key const char* lookup(Dictionary* dict, const char* key) unsigned int index = hash_function(key); Node* temp = dict->buckets[index]; while (temp != NULL) if (strcmp(temp->key, key) == 0) return temp->value; temp = temp->next; return NULL; // Key not found // Delete a key-value pair from the dictionary int delete_key(Dictionary* dict, const char* key) unsigned int index = hash_function(key); Node* temp = dict->buckets[index]; Node* prev = NULL; while (temp != NULL) if (strcmp(temp->key, key) == 0) if (prev == NULL) // Node to delete is the head of the list dict->buckets[index] = temp->next; else // Node to delete is in the middle or end prev->next = temp->next; free(temp->key); free(temp->value); free(temp); return 1; // Success prev = temp; temp = temp->next; return 0; // Key not found Use code with caution.

prev = entry; entry = entry->next;

return d;

printf("Inserted ('%s', %d) at index %u\n", key, value, idx);

int main() Dictionary myDict = 0 ; // Initialize buckets to NULL insert(&myDict, "Apple" , "A sweet red fruit" ); insert(&myDict, "C" , "A powerful programming language" ); char *result = search(&myDict, "Apple" ); if (result) printf( "Apple: %s\n" , result); return 0 ; Use code with caution. Copied to clipboard Quick Way to Implement Dictionary in C - Stack Overflow

while (current != NULL) if (strcmp(current->key, key) == 0) if (prev == NULL) // Node is at the head dict->table[index] = current->next; else // Node is in the middle or end prev->next = current->next; To implement a robust dictionary in C using

for basic operations. This article explores how to implement a fully functional dictionary in C using hashing algorithms and chaining for collision resolution. Core Concepts of Hashing

💡 : Faster than Binary Search Trees for lookups.💡 Memory : More efficient than huge arrays when keys are non-integer strings.💡 Flexibility : Can be easily adapted to store any data type (integers, floats, or custom objects). If you'd like to refine this, A more advanced hash function like DJB2. Code to delete items from the dictionary. Share public link

For string keys, the algorithm created by Dan Bernstein is an excellent choice. It is a simple, fast bit-shift hashing function that distributes strings uniformly across the hash table, drastically reducing collisions. The mathematical formula for DJB2 is: