PSET5 Speller hash function

Question

I have been working on the speller problem in pset5 for a while now, and I am not able to figure out the problem in my hash function:

unsigned int hash(const char* word)
{
    int M = 1000000001;
    int P = 31;
    int hash_value = 0;
    int p_pow = 1;

    int len = strlen(word);

    for (int i = 0; i < len; i++)
    {
        hash_value = (hash_value + (word[i] - 'a' + 1) * p_pow) % M;
        p_pow = (p_pow * P) % M;
    }
    return hash_value;
}

Source : https://cp-algorithms.com/string/string-hashing.html

If I run my program with this hash function, following errors come on doing check50

:) dictionary.c, dictionary.h, and Makefile exist
:) speller compiles
:( handles most basic words properly
     expected "MISSPELLED WOR...", not ""
:) handles min length (1-char) words
:( handles max length (45-char) words
     expected "MISSPELLED WOR...", not ""
:( handles words with apostrophes properly
     expected "MISSPELLED WOR...", not "MISSPELLED WOR..."
:) spell-checking is case-insensitive
:( handles substrings properly
     expected "MISSPELLED WOR...", not ""
:| program is free of memory errors
     can't check until a frown turns upside down

Whereas if I use any other hash function, such as:

unsigned int hash(const char* word)
{
        unsigned int hash_value = 0;
        for (int i = 0, n = strlen(word); i < n; i++)
        {
             hash_value = (hash_value << 2) ^ word[i];
        }
        return hash_value % N; //N is size of hashtable
}

The program compiles correctly with everything green.
Since both the hash functions should work fine, I am confused why the first one is not working properly.

Any help would be kindly appreciated.

Answer 1

Just use the one that works that simple. The reason we were told to just get hash functions from the internet is because hash functions are hard to make, so most probably the design of the function that works, works better in this situation than the other one.

Answer 2

can i ask what value ur N was?