hashmap_C

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

#define TABLE_SIZE 1000

struct pair
{
    char *key;
    int value;
    struct pair *next;
};

struct hashmap
{
    struct pair *table[TABLE_SIZE];
};

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

    while ((c = *str++))
    {
        hash = ((hash << 5) + hash) + c;
    }

    return hash % TABLE_SIZE;
}

struct hashmap *create_map()
{
    struct hashmap *map = malloc(sizeof(struct hashmap));
    memset(map, 0, sizeof(struct hashmap));
    return map;
}

void put(struct hashmap *map, char *key, int value)
{
    unsigned long index = hash(key);

    struct pair *pair = map->table[index];
    while (pair != NULL)
    {
        if (strcmp(pair->key, key) == 0)
        {
            pair->value = value;
            return;
        }
        pair = pair->next;
    }

    pair = malloc(sizeof(struct pair));
    pair->key = strdup(key);
    pair->value = value;
    pair->next = map->table[index];
    map->table[index] = pair;
}

int get(struct hashmap *map, char *key)
{
    unsigned long index = hash(key);

    struct pair *pair = map->table[index];
    while (pair != NULL)
    {
        if (strcmp(pair->key, key) == 0)
        {
            return pair->value;
        }
        pair = pair->next;
    }

    return -1;
}

void remove_key(struct hashmap *map, char *key)
{
    unsigned long index = hash(key);

    struct pair *pair = map->table[index];
    struct pair *prev = NULL;
    while (pair != NULL)
    {
        if (strcmp(pair->key, key) == 0)
        {
            if (prev == NULL)
            {
                map->table[index] = pair->next;
            }
            else
            {
                prev->next = pair->next;
            }
            free(pair->key);
            free(pair);
            return;
        }
        prev = pair;
        pair = pair->next;
    }
}

void print_map(struct hashmap *map)
{
    for (int i = 0; i < TABLE_SIZE; i++)
    {
        struct pair *pair = map->table[i];
        while (pair != NULL)
        {
            printf("%s: %d\n", pair->key, pair->value);
            pair = pair->next;
        }
    }
}

int main()
{
    struct hashmap *map = create_map();

    put(map, "one", 1);
    put(map, "two", 2);
    put(map, "three", 3);
    put(map, "four", 4);
    put(map, "five", 5);

    printf("Value of key 'two': %d\n", get(map, "two"));

    remove_key(map, "three");

    printf("Map contents:\n");
    print_map(map);

    return 0;
}