What data structure should I use for hierarchical data?

please help:

I have a data set need to be stored like tree, following is stucture, I am not sure how to store this, the letters are开发者_JS百科 not comparable, this is just a hierarchic structure

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From the picture, this just looks like a binary tree where only the leaf nodes contain data. So, use a binary tree and only put data in the leaf nodes.