CS50 pset5 SPELLER - most basic words & substrings issues - cs50

Question

I have been stuck in pset5 for a while now. No matter from which angle I look to my code I cannot fin out what is wrong with it. I set my number of buckets randomly to 1000. Can someone find out the problem?
Below is the reply I get from check50
:) dictionary.c, dictionary.h, and Makefile exist
:) speller compiles
:( handles most basic words properly
expected "MISSPELLED WOR...", not "MISSPELLED WOR..."
:) handles min length (1-char) words
:) handles max length (45-char) words
:) handles words with apostrophes properly
:) spell-checking is case-insensitive
:( handles substrings properly
expected "MISSPELLED WOR...", not "MISSPELLED WOR..."
:| program is free of memory errors
can't check until a frown turns upside down
these is what I've done:
const unsigned int N = 1000;
// Returns true if word is in dictionary else false
bool check(const char *word)
{
//convert *word to lowercase so that the hash function is case-insensitive
int length = strlen(word);
char copy[length + 1];
for (int i = 0; i < length; i++)
{
copy[i] = tolower(word[i]);
}
// create a variable to return hashed value of word
int index_check = hash(copy);
//create cursor to traverse the linked list
node *cursor = table[index_check];
//check if word is in the linked list
while (cursor != NULL)
{
if (strcasecmp(word, cursor->word) == 0)
{
return true;
}
cursor = cursor->next;
}
//return false if cursor->next = NULL has been reached
return false;
}
// Hashes word into a number
unsigned int hash(const char *word)
{
// Source of hash function: stackoverflow.com/questions/14409466/simple-hash-functions
unsigned int count;
unsigned int hashValue = 0;
for(count = 0; word[count] != '\0'; count++)
{
hashValue = word[count] + (hashValue << 6) + (hashValue << 16) - hashValue;
}
return (hashValue % N);
}
// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)
{
// open dictionary file
FILE *f = fopen(dictionary, "r");
if (f == NULL)
{
printf("Dictionary could not be opened\n");
return false;
}
//initialize string as a buffer, to be used in next function, fscanf
char buffer[LENGTH + 1];
//loop to check whether end of file has been reached
while (fscanf(f, "%s", buffer) != EOF)
{
//read words from file into buffer
fscanf(f, "%s", buffer);
//allocate memory for a node and check if NULL
node *n = malloc(sizeof(node));
if (n == NULL)
{
printf("Could not allocate memmory (malloc *n)\n");
return false;
}
//copy "buffer" into the node created
strcpy(n->word, buffer);
//call hash function
int index = hash(buffer);
//check if it's the first word being inserted into that bucket
if (table[index] == NULL)
{
table[index] = n;
}
else
{
n->next = table[index];
table[index] = n;
}
size_dictionary++;
}
fclose(f);
return true;
}
// Unloads dictionary from memory, returning true if successful else false
bool unload(void)
{
node *cursor;
node *tmp;
// run thru all buckets
for(int i = 0; i < N; i++)
{
//check if bucket isn't NULL
if(table[i] != NULL)
{
cursor = table[i];
tmp = cursor;
while (tmp != NULL)
{
cursor = cursor->next;
free(tmp);
tmp = cursor;
}
}
}
return true;
}

Answer 1

The clue is in WORDS IN DICTIONARY. Only half the words in dictionary are loaded. That is because of the back-to-back fscanf in load.

Answer 2

tiagoK, I think I'm having the same issue here and been stuck with this exercice for days. What did you mean by " the loop should have been done with lenght + 1", where did you declare this string ? I've tried it on the strcasecmp field and the hash one but it doesn't change anything. Do you remember ?
#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include "dictionary.h"
// Represents a node in a hash table
typedef struct node
{
char word[LENGTH + 1];
struct node *next;
}
node;
// Choose number of buckets in hash table
const unsigned int N = 17576;
// Hash table
node *table[N];
// Initialize new variables used in the program
unsigned int numberofwords;
unsigned int hashvalue;
// Returns true if word is in dictionary, else false
bool check(const char *word)
{
// Hash the word to determine its hash value
hashvalue = hash(word);
// Set cursor to the head of the linked list of the word
node* cursor = table[hashvalue];
// Traverse into the linked list comparing the word to find a correspondance while the cursor isn't pointing to null
while (cursor != NULL)
{
if (strcasecmp(cursor->word, word) == 0)
{
return true;
}
cursor = cursor->next;
}
return false;
}
// Hashes word to a number
unsigned int hash(const char *word)
{
// Inittialize a variable to keep track of the total of ASCII values
unsigned int sum = 0;
// Loop in all the letters in the word
for (int i = 0 ; i < strlen(word) ; i++)
{
// Ignore digits
if (isdigit(word[i]))
{
continue;
}
else if (isalpha(word[i]) || word[i] == ('\''))
{
// Check the first three character in the word while setting them lower letters in order to get they ASCII value
sum += tolower(word[0] - 'a');
sum += tolower(word[1] - 'a');
sum += tolower(word[2] - 'a');
}
}
// Divide the total of the three letters by the number of buckets
hashvalue = sum % N;
return hashvalue;
}
// Loads dictionary into memory, returning true if successful, else false
bool load(const char *dictionary)
{
// Open the file
FILE* file = fopen(dictionary, "r");
char word[LENGTH + 1];
{
if (file != NULL)
{
// While dictionary doesn't return EOF, read strings from the file, one at the time
while (fscanf(file, "%s", word) != EOF)
{
// Create a new node for the word and copy it in the node
node *n = malloc(sizeof(node));
if (n == NULL)
{
return 1;
}
strcpy (n->word, "%s");
// Hash word to obtain a hash value
hashvalue = hash(word);
// Insert word into hash table depending if it's the first word or not
if (table[hashvalue] != NULL)
{
n->next = table[hashvalue];
}
else
{
n->next = NULL;
}
table[hashvalue] = n;
// Add one to the counter
numberofwords++;
}
fclose(file);
}
else
{
fclose(file);
perror("Loading error");
return 1;
}
}
// Return true
return true;
}
// Returns number of words in dictionary if loaded, else 0 if not yet loaded
unsigned int size(void)
{
// Return the number of words we're keeping track of while loading the dictionary
return numberofwords;
}
// Unloads dictionary from memory, returning true if successful, else false
bool unload(void)
{
// Check all the head of the hash table
for(int i = 0; i < N; i++)
{
// Create a temporary node to not lose the rest of the linked list
node* cursor = table[i];
// Set the cursor to the next node while the temporary value remains at the inital location, then free it before to move to cursor
while(cursor != NULL)
{
node* tmp = cursor;
cursor = cursor->next;
free(tmp);
}
}
return true;
}