My implementation of `dictionary.c` from CS50's speller week 5 problem

dictionary.c

// Implements a dictionary's functionality

#include <ctype.h>
#include <stdbool.h>
#include <strings.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "dictionary.h"

// Represents a node in a hash table
typedef struct node
{
    char word[LENGTH + 1];
    struct node *next;
}
node;

// TODO: Choose number of buckets in hash table
const unsigned int N = 26;

//count variable
int count = 0;

// Hash table
node *table[N];

// Returns true if word is in dictionary, else false
bool check(const char *word)
{
    // TODO
    //hash word to obatain a hash value
    int hashed = hash(word);

    //Access linked list at that index
    node *n = table[hashed];
    if (n == NULL)
    {
        return 1;
    }

    //Traverse linked list looking for new word
    while (n != NULL)
    {
        if (strcasecmp(n->word, word) == 0)
    {
        return true;
    }
    n = n -> next;
    }
    return false;
}

// Hashes word to a number
unsigned int hash(const char *word)
{
    // TODO: Improve this hash function
    unsigned int num = 0;
    //loop through each word
    for (int i = 0; i < strlen(word); i++)
     {
        // num += toupper(word[i] - 'A');
        //capitalise each word and multiply by
        num += toupper(word[i] * 26) * num;
     }
     num = num % N;
    return num;
}

// Loads dictionary into memory, returning true if successful, else false
bool load(const char *dictionary)
{
    // TODO
    //Open dictionary file
    FILE *file = fopen(dictionary, "r");
    //check null
    if (dictionary == NULL)
    {
        printf("Could not open%s\n", dictionary);
        return 1;
    }
    char buffer[LENGTH + 1];

    //read strings from file into buffer
    while (fscanf(file, "%s", buffer) != EOF)
    {
        //allocate space and create new node for each word
        node *n = malloc(sizeof(node));
        //check for NULL
        if (n == NULL)
        {
            return 1;
        }
        //copy word into node using strcpy
        strcpy(n->word, buffer);
        n->next = NULL;

        //Use the hash function to hash words
        int hashed = hash(buffer);

        //set node pointer to current head
        n->next = table[hashed];
        //then set head to point to the new node
        table[hashed] = n;
        count++;
    }
    fclose(file);
    return true;
}

// Returns number of words in dictionary if loaded, else 0 if not yet loaded
unsigned int size(void)
{
    // TODO
    return count;
}

// Unloads dictionary from memory, returning true if successful, else false
bool unload(void)
{
    // TODO
    //loop over hash tables
    for (int i = 0; i < N; i++)
    {
        //set cursor to first item in node
        node *cursor = table[i];

         //keep moving cursor until you get to NULL
        while(cursor != NULL)
        {
            //assign temporary node
            node *tmp = cursor;
            cursor = cursor->next;
            //free up memory
            free(tmp);
        }
        if (cursor == NULL)
        {
            if (i == N - 1)
            {
                return true;
            }
        }
    }
    return false;
}

dictionary.h

// Declares a dictionary's functionality

#ifndef DICTIONARY_H
#define DICTIONARY_H

#include <stdbool.h>

// Maximum length for a word
// (e.g., pneumonoultramicroscopicsilicovolcanoconiosis)
#define LENGTH 45

// Prototypes
bool check(const char *word);
unsigned int hash(const char *word);
bool load(const char *dictionary);
unsigned int size(void);
bool unload(void);

#endif // DICTIONARY_H

speller.c

// Implements a spell-checker

#include <ctype.h>
#include <stdio.h>
#include <sys/resource.h>
#include <sys/time.h>

#include "dictionary.h"

// Undefine any definitions
#undef calculate
#undef getrusage

// Default dictionary
#define DICTIONARY "dictionaries/large"

// Prototype
double calculate(const struct rusage *b, const struct rusage *a);

int main(int argc, char *argv[])
{
    // Check for correct number of args
    if (argc != 2 && argc != 3)
    {
        printf("Usage: ./speller [DICTIONARY] text\n");
        return 1;
    }

    // Structures for timing data
    struct rusage before, after;

    // Benchmarks
    double time_load = 0.0, time_check = 0.0, time_size = 0.0, time_unload = 0.0;

    // Determine dictionary to use
    char *dictionary = (argc == 3) ? argv[1] : DICTIONARY;

    // Load dictionary
    getrusage(RUSAGE_SELF, &before);
    bool loaded = load(dictionary);
    getrusage(RUSAGE_SELF, &after);

    // Exit if dictionary not loaded
    if (!loaded)
    {
        printf("Could not load %s.\n", dictionary);
        return 1;
    }

    // Calculate time to load dictionary
    time_load = calculate(&before, &after);

    // Try to open text
    char *text = (argc == 3) ? argv[2] : argv[1];
    FILE *file = fopen(text, "r");
    if (file == NULL)
    {
        printf("Could not open %s.\n", text);
        unload();
        return 1;
    }

    // Prepare to report misspellings
    printf("\nMISSPELLED WORDS\n\n");

    // Prepare to spell-check
    int index = 0, misspellings = 0, words = 0;
    char word[LENGTH + 1];

    // Spell-check each word in text
    char c;
    while (fread(&c, sizeof(char), 1, file))
    {
        // Allow only alphabetical characters and apostrophes
        if (isalpha(c) || (c == '\'' && index > 0))
        {
            // Append character to word
            word[index] = c;
            index++;

            // Ignore alphabetical strings too long to be words
            if (index > LENGTH)
            {
                // Consume remainder of alphabetical string
                while (fread(&c, sizeof(char), 1, file) && isalpha(c));

                // Prepare for new word
                index = 0;
            }
        }

        // Ignore words with numbers (like MS Word can)
        else if (isdigit(c))
        {
            // Consume remainder of alphanumeric string
            while (fread(&c, sizeof(char), 1, file) && isalnum(c));

            // Prepare for new word
            index = 0;
        }

        // We must have found a whole word
        else if (index > 0)
        {
            // Terminate current word
            word[index] = '\0';

            // Update counter
            words++;

            // Check word's spelling
            getrusage(RUSAGE_SELF, &before);
            bool misspelled = !check(word);
            getrusage(RUSAGE_SELF, &after);

            // Update benchmark
            time_check += calculate(&before, &after);

            // Print word if misspelled
            if (misspelled)
            {
                printf("%s\n", word);
                misspellings++;
            }

            // Prepare for next word
            index = 0;
        }
    }

    // Check whether there was an error
    if (ferror(file))
    {
        fclose(file);
        printf("Error reading %s.\n", text);
        unload();
        return 1;
    }

    // Close text
    fclose(file);

    // Determine dictionary's size
    getrusage(RUSAGE_SELF, &before);
    unsigned int n = size();
    getrusage(RUSAGE_SELF, &after);

    // Calculate time to determine dictionary's size
    time_size = calculate(&before, &after);

    // Unload dictionary
    getrusage(RUSAGE_SELF, &before);
    bool unloaded = unload();
    getrusage(RUSAGE_SELF, &after);

    // Abort if dictionary not unloaded
    if (!unloaded)
    {
        printf("Could not unload %s.\n", dictionary);
        return 1;
    }

    // Calculate time to unload dictionary
    time_unload = calculate(&before, &after);

    // Report benchmarks
    printf("\nWORDS MISSPELLED:     %d\n", misspellings);
    printf("WORDS IN DICTIONARY:  %d\n", n);
    printf("WORDS IN TEXT:        %d\n", words);
    printf("TIME IN load:         %.2f\n", time_load);
    printf("TIME IN check:        %.2f\n", time_check);
    printf("TIME IN size:         %.2f\n", time_size);
    printf("TIME IN unload:       %.2f\n", time_unload);
    printf("TIME IN TOTAL:        %.2f\n\n",
           time_load + time_check + time_size + time_unload);

    // Success
    return 0;
}

// Returns number of seconds between b and a
double calculate(const struct rusage *b, const struct rusage *a)
{
    if (b == NULL || a == NULL)
    {
        return 0.0;
    }
    else
    {
        return ((((a->ru_utime.tv_sec * 1000000 + a->ru_utime.tv_usec) -
                  (b->ru_utime.tv_sec * 1000000 + b->ru_utime.tv_usec)) +
                 ((a->ru_stime.tv_sec * 1000000 + a->ru_stime.tv_usec) -
                  (b->ru_stime.tv_sec * 1000000 + b->ru_stime.tv_usec)))
                / 1000000.0);
    }
}