Glad to help, and please feel free to ask :-) You can add the same debugging statements as in my first piece of code (at the bottom of the post), then you can hopefully see how everything is being transformed. If I were to nitpick my own code, I would probably add some checking that all the inputs are in the expected formats (e.g. use a regex instead of split). And the updated piece of code depends on the original array not changing, since it creates a second list of indicies.