A Common-Sense Guide to Data Structures and Algorithms, Second Edition, 2nd Edition

Filesystem Traversal

Now that you’ve seen how recursion works, we can use it to solve certain problems that would otherwise be uncrackable.

One type of problem in which recursion is a natural fit is when we need to delve into multiple layers of a problem without knowing how many layers there are.

Take the example of traversing through a filesystem. Let’s say you have a script that does something with all the contents inside a directory, such as printing all the subdirectory names. However, you don’t want the script to only handle the immediate subdirectories—you want it to act on all the subdirectories within the subdirectories of the directory and all of their subdirectories, and so on.

Let’s create a simple Ruby script that prints the names ...