Question

I couldn’t find anything similar to this anywhere. I have an array of pointers to objects (a linked list) for a hash table:

LinkList * table[TABLE_SIZE];
for (int i = 0; i < TABLE_SIZE; i++)
    table[i] = NULL;

In one of my functions for my hash table class, there I need to call the one of the functions on the LinkList object in the table array. I’m calling it as such:

void HashMap::add_customer(string first, string last, string phone) {   
    int hash = get_hash(phone);
    if (table[hash] == NULL) {
        table[hash] = new LinkList;
    }
    table[hash]->add_customer(first, last, phone); // I HATE THIS LINE
}

Everything compiles fine, but when I execute the table[hash]->add_customer() line in runtime, I get a Segmentation Fault error. When this line is commented out, I get no errors, but obviously, I can’t add any customers to my hash table. Is this not the right syntax?

Answer 1

You have to initialized your array of pointers to NULL, since they’ll be allocated on the stack/heap or wherever with junk values ….

LinkList * table[TABLE_SIZE];
memset(table, NULL, sizeof(LinkList *) * TABLE_SIZE);

assuming you’ve initialized correctly then please check your hashes and assert that indeed they are hash < TABLE_SIZE

try this:

 int hash = get_hash(phone) % TABLE_SIZE;