Hashmap

hashmap.c

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

#define MAX_KEY 50
#define MAX_HASH 10

struct node {
     char key[MAX_KEY];
     int value;
     struct node* next;
};

/* Adds up char values of key and then does a modulus on the hash size */
int hash_func (char key[], int hash_max)
{
     int total = 0;
     int len;
     len = strlen(key);

     int i;
     for (i = 0; i < len; i++)
          total += (int) key[i];

     return total % hash_max;
}

/* constructs a new node and puts it into the array at the head of the linked list */
int put_int (struct node* hash_array[], int hash_max, char key[], int value)
{
     int index = hash_func(key, hash_max);
     struct node* new = malloc(sizeof(struct node));

     printf("Putting %s into hash at index %d\n", key, index);

     new->value = value;
     strcpy(new->key, key);
     new->next = hash_array[index];
     hash_array[index] = new;
     return 0;
}

/* goes through linked list at the index and outputs the int if it exists */
int* get_int_ptr (struct node* hash_array[], int hash_max, char key[])
{
     int index = hash_func(key, hash_max);
     struct node* curr = hash_array[index];

     printf("Looking for %s in hash\n", key);

     while (curr != NULL) {
          printf("At node with key %s and value %d\n", curr->key, curr->value);

          if (strcmp(curr->key, key) == 0) {
               int* ans;
               ans = &(curr->value);

               return ans;
          } else 
               curr = curr->next;
     }

     return NULL;
}

/* fills a hash array with empty structs */
int init_hash (struct node* hash_array[], int hash_max)
{
     struct node* empty = malloc(sizeof(struct node));

     empty->key[0] = '\0';
     empty->value = 0;
     empty->next = NULL;
   
     int i;
     for (i = 0; i < hash_max; i++)
               hash_array[i] = empty;
    
     return 0;
}

int main ()
{
     /* make and init hash array */
     struct node* hash_array[MAX_HASH];
     init_hash(hash_array, MAX_HASH);

     /* put some values in.  two and three go to same bucket */
     put_int(hash_array, MAX_HASH, "one", 1);
     put_int(hash_array, MAX_HASH, "two", 2);
     put_int(hash_array, MAX_HASH, "three", 3);

     /* get an int pointer back as answer */
     int* ans_ptr = get_int_ptr(hash_array,  MAX_HASH, "two");

     /* make sure it isn't null */
     if (ans_ptr != NULL) {
          int ans = *ans_ptr;
          printf("%d\n", ans);
     } else
          printf("Not found\n");

     return 0;
}