TechTree - Way to store the data?


I’m trying to make a node tree, however I can’t seem to figure out the best way to store the data. Here’s the tech tree I want to store.

The first thing that comes to mind, is to store them as an array. So, an array within an array, withing another array for however many levels deep my tech trees go.

Now that would work… if not for the centre node which has 2 parent nodes that point to it.

How else could I store this data?