title: What data structure should I use for hierarchical data?
body: <p>please help:</p>
  
  <p>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 not comparable, this is just a hierarchic structure
  <img src="https://i.stack.imgur.com/81N92.jpg" alt="alt text"></p>