C Program To Implement Dictionary Using Hashing Algorithms -

Report: Dictionary Implementation Using Hashing Algorithms in C

1. Abstract

This report presents the design and implementation of a dictionary data structure in the C programming language using hashing techniques. A dictionary, also known as a symbol table or associative array, stores key-value pairs and supports efficient insertion, search, and deletion operations. Hashing provides average-case O(1) time complexity for these operations. This implementation uses separate chaining to handle collisions and a simple polynomial rolling hash function for strings.

Common Pitfalls

• Memory leaks - Always free keys and entries
• Modifying keys after insertion - Keys should be immutable
• Poor hash distribution - Test your hash function with expected data
• Ignoring load factor - Leads to degraded performance

If you use an array (sorted), search is O(log n) with binary search, but insert/delete are O(n). If you use a linked list, search is O(n). Hashing transforms this by using a hash function to convert the key into an integer index, allowing direct access to an array slot. In an ideal scenario, all operations are O(1). c program to implement dictionary using hashing algorithms

unsigned long hash_crc(const char *str) 
    unsigned long hash = 0xFFFFFFFF;
    int c;
    while ((c = *str++)) 
        hash = (hash >> 8) ^ crc32_table[(hash ^ c) & 0xFF];
typedef struct Dictionary 
    Entry **buckets;    // Array of pointers to linked lists
    unsigned long size; // Current number of buckets
    unsigned long count; // Number of key-value pairs stored
    unsigned long (*hash_func)(const char *); // Function pointer for hash algorithm
 Dictionary;


Alternative: FNV-1a hash (better distribution): Memory leaks - Always free keys and entries
return hash_value % table_size;