Class 47: Trees, Continued

Held Tuesday, November 21, 2000

Summary

Today we continue our investigation of trees by building a tree interface and considering possible implementations.

Notes

• How did yesterday's class go?
• I'm working on the third exam and it will be ready before class tomorrow.
  • Almost no code writing required, so that you can work on it during Thanksgiving break.
  • And yes, I'm sorry that I've become of the faculty who assign work during Thanksgiving break.
• Today's class outline is intentionally vague; I'd like to have you think about many of these issues without relying on my perspectives.
• Observations about interviewing process

Overview

• Review
• Designing a general tree interface
• Implementing that interface

Review

• Tell me what you learned.
• Tell me what you want to learn.
• What applications do we have for trees?
• Should trees really be an ADT, or are they simply a data structure with no underlying ADT?

Interface

• Suppose we were designing our own tree interface from scratch. What design choices should we make? (Assume n-ary as opposed to binary.)
• Can we have "gaps" in the children? (E.g., a 1st and 4th child, but not a second or third?)
• Do we need tree cursors?
  • If so, does a tree have one cursor, or can you create multiple separate cursors?
• If we don't use tree cursors, what are the alternates?
• Once we've set a value in a tree, should we be able to mutate it?
• ...

Implementation

• If we use nodes, what goes in our TreeNode class?
  • Do we want a parent field?
  • What field or fields should we use for children?
• Are there other implementations? (Yes, but can you think of any?)