Implement Hash Table using Arrays

#include <stdio.h>
#include <stdlib.h>

#define TABLE_SIZE 10

// Define the structure of each element in the hash table
typedef struct {
    int key;
    int value;
    int is_occupied; // 0 means empty, 1 means occupied
} HashItem;

// Initialize the hash table as an array
HashItem hashTable[TABLE_SIZE];

// Hash function to map keys to indices
int hashFunction(int key) {
    return key % TABLE_SIZE;
}

// Function to insert a key-value pair into the hash table
void insert(int key, int value) {
    int index = hashFunction(key);

    // Use linear probing in case of collision
    while (hashTable[index].is_occupied) {
        if (hashTable[index].key == key) {
            // If key already exists, update the value
            hashTable[index].value = value;
            printf("Updated key %d with value %d at index %d\n", key, value, index);
            return;
        }
        index = (index + 1) % TABLE_SIZE; // Move to the next index
    }

    // Insert the new key-value pair
    hashTable[index].key = key;
    hashTable[index].value = value;
    hashTable[index].is_occupied = 1; // Mark as occupied
    printf("Inserted key %d with value %d at index %d\n", key, value, index);
}

// Function to search for a value by its key in the hash table
int search(int key) {
    int index = hashFunction(key);

    // Use linear probing to search for the key
    while (hashTable[index].is_occupied) {
        if (hashTable[index].key == key) {
            // If key is found, return the value
            return hashTable[index].value;
        }
        index = (index + 1) % TABLE_SIZE; // Move to the next index
    }

    // If key is not found, return -1
    return -1;
}

// Function to delete a key-value pair from the hash table
void delete(int key) {
    int index = hashFunction(key);

    // Use linear probing to find the key
    while (hashTable[index].is_occupied) {
        if (hashTable[index].key == key) {
            // Mark the slot as empty
            hashTable[index].is_occupied = 0;
            printf("Deleted key %d from index %d\n", key, index);
            return;
        }
        index = (index + 1) % TABLE_SIZE; // Move to the next index
    }

    printf("Key %d not found for deletion\n", key);
}

// Function to display the hash table
void display() {
    printf("Hash Table:\n");
    for (int i = 0; i < TABLE_SIZE; i++) {
        if (hashTable[i].is_occupied) {
            printf("Index %d: Key %d, Value %d\n", i, hashTable[i].key, hashTable[i].value);
        } else {
            printf("Index %d: Empty\n", i);
        }
    }
}

// Main function to test the hash table
int main() {
    // Initialize the hash table slots as empty
    for (int i = 0; i < TABLE_SIZE; i++) {
        hashTable[i].is_occupied = 0;
    }

    // Insert some key-value pairs
    insert(1, 10);
    insert(11, 20);
    insert(21, 30);
    insert(31, 40);

    // Display the hash table
    display();

    // Search for a key
    int key = 11;
    int result = search(key);
    if (result != -1) {
        printf("Value for key %d: %d\n", key, result);
    } else {
        printf("Key %d not found in hash table\n", key);
    }

    // Delete a key
    delete(11);
    display();

    return 0;
}