Question

Our class is learning about hash tables, and one of my study questions involves me creating a dictionary using a hash table with separate chaining. However, the catch is that we are not allowed to use Java’s provided methods for creating hash tables. Rather, our lecture notes mention that separate chaining involves each cell in an array pointing to a linked list of entries.

Thus, my understanding is that I should create an array of size n (where n is prime), and insert an empty linked list into each position in the array. Then, I use my hash function to hash strings and insert them into the corresponding linked list in the proper array position. I created my hash function, and so far my Dictionary constructor takes in a size and creates an array of that size (actually, of size 4999, both prime and large as discussed in class). Am I on the right track here? Should I now insert a new linked list into each position and then work on insert/remove methods?

Answer 1

What you have sounds good so far.

Bear in mind that an array of object references has each cell null by default, and you can write your insert and remove functions to work with that. If you choose to create a linked list object that contains no data (sometimes called a sentinel node) it may be advantageous to create a single immutable (read-only) instance to put in every empty slot, rather than create 4,999 separate instances with new (where most don’t hold any data).