Question

I am having a lot of trouble with this task. Using the Wikipedia definition for a complete binary tree:

A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible

I need a way of checking for these conditions, but no matter how much I try, I can’t seem to come up with anything. If I were to pass a TreeNode tree input into a checkComplete method how could I go about going through the binary tree and checking that it is complete? Can anyone help with pseudocode or an explanation of how this is possible? There was another question here: How to determine whether a binary tree is complete?

This one had an answer with pseudocode in it, but I couldn’t understand where all the random variables were coming from or what they were meant to represent or why there were two values in brackets in the last 3 lines. If anyone could help with another representation I’d really appreciate it.

Answer 1

Traverse the tree left-to-right. There are several critical points at which you’ll want to store or compare information:

• When you hit the first leaf node.
• When you hit subsequent leaf nodes.
• When you hit the first leaf node with a different distance from the root.

Since this is homework, you should probably take it the rest of the way from that hint.