What would you do differently if you had more time?
I would setup the task to execute at the start of each day.

What is the runtime complexity of each function?
I did not do it due to lack of time.

How does your code work?
I created a home controller that when you visit the page it saves your ip address in a hash (in memory), your ip address is the key and the value is the visits counter.

Also, I created a view that when you visit it shows the top 100 IP addressess by request count. Finally, I created a task to run a method called clear_ips that clears the created hash.

What other approaches did you decide not to pursue?
Setup the time to execute the task.

How would you test this?
I would use an script with python (maybe) to simulate requests with diferent ips.