Swift Algorithm Club: Hash Tables

Resizing the Hash Table

This version of the hash table always uses an array of fixed size or capacity. If you have many items to store in the hash table, choose a prime number greater than the maximum number of items.

The load factor of a hash table is the percentage of the capacity that is currently used. If there are 3 items in a hash table with 5 buckets, then the load factor is 3/5 = 60%.

If the hash table is small, and the chains are long, the load factor can become greater than 1, which is a sign of bad performance. One way to avoid this is to resize the hash table. Adding the code for this condition is left as an exercise for the reader. Keep in mind that making the buckets array larger will change the array indices that the keys map to! This requires you to insert all the elements again after resizing the array.

Where to Go From Here?

I hope you enjoyed this tutorial on implementing a Swift hash table!

Here is a playground with the above code. You can also find the original implementation here.

This was just one of the many algorithms in the Swift Algorithm Club repository. If you're interested in more, check out the repo.

It's in your best interest to know about algorithms and data structures - they're solutions to many real-world problems, and are frequently asked as interview questions. Plus it's fun!

So stay tuned for many more tutorials from the Swift Algorithm club in the future. In the meantime, if you have any questions on implementing trees in Swift, please join the forum discussion below.

If you enjoyed what you learned in this tutorial, why not check out our Data Structures and Algorithms in Swift book, available on our store?

In Data Structures and Algorithms in Swift, you’ll learn how to implement the most popular and useful data structures and when and why you should use one particular datastructure or algorithm over another. This set of basic data structures and algorithms will serve as an excellent foundation for building more complex and special-purpose constructs.

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