C Hash Functions 🎯

Welcome to our deep dive into C Hash Functions! This lesson is designed to help both beginners and intermediates understand and apply hash functions in C programming. Let's embark on this exciting journey together! 🚀

What are Hash Functions? 📝

Hash functions are essential tools in computer science, particularly in areas like data structures and cryptography. They transform data of arbitrary size into a fixed-size representation (a hash value or hash code). This transformation is deterministic, meaning the same input will always produce the same output.

Hash functions are crucial because they allow us to quickly search large datasets, identify duplicates, and ensure data integrity.

Why Hash Functions? 💡

Hash functions simplify complex operations. For instance, in a dictionary, instead of searching through each word (which could take a long time for large dictionaries), we can use a hash function to quickly find the word's location. This makes the process more efficient!

Hash Function Basics in C 🎯

In C, we create custom hash functions using basic operations. A common type for hash functions is unsigned int.

unsigned int myHashFunction(char *str) {
    unsigned int hash = 5381;
    int c;

    while ((c = *str++))
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */

    return hash % TABLE_SIZE;
}

💡 Pro Tip: This simple hash function uses a technique called Hashing with a universal hash function to ensure good distribution of the strings in the table.

Practical Application 🎯

Let's create a simple hash table to store unique words.

#include <stdio.h>
#define TABLE_SIZE 1000

unsigned int myHashFunction(char *str);

int main() {
    char str[100];
    int slots[TABLE_SIZE] = { 0 };
    unsigned int i;

    while (scanf("%s", str) == 1) {
        i = myHashFunction(str);
        if (!slots[i])
            slots[i] = 1;
        else
            printf("Duplicate: %s\n", str);
    }

    return 0;
}

Quiz Time! 🎯

Stay tuned for the next lesson, where we'll delve deeper into hash tables and explore more advanced hash function techniques! 🌟