Log in from a computer to take this course

You'll need to log in from a computer to start Introduction to Algorithms and Linear Data Structures in Swift. But you can practice or keep up your coding streak with the Codecademy Go app. Download the app to get started.

apple storegoogle store
Learn

We’ve learned together what a hash map is and how to create one. Let’s go over the concepts presented in this lesson.

A hash map is:

  • Built on top of an array using a special indexing system.
  • A key-value storage with fast assignments and lookup.
  • A table that represents a map from a set of keys to a set of values.

Hash maps accomplish all this by using a hash function, which turns a key into an index into the underlying array.

A hash collision is when a hash function returns the same index for two different keys.

There are different hash collision strategies. Two important ones are separate chaining, where each array index points to a different data structure, and open addressing, where a collision triggers a probing sequence to find where to store the value for a given key.

Instructions

What makes good data to save into a hash map? Can you think of instances where a hash map would help you solve a problem faster?

Take this course for free

Mini Info Outline Icon
By signing up for Codecademy, you agree to Codecademy's Terms of Service & Privacy Policy.

Or sign up using:

Already have an account?