Interesting.

For short trees and in-memory management another option would be:

  electronics
  /televisions
  //tube
  //lcd
  //plasma
  /portable electronics
  //mp3 players
  ///flash
  //cd players
  //2 way radios

Where depth levels are represented by slashes only.

Replace with indexes and you have a shorter version.

Let's see what else we can come up with just for fun...