Solve: Binary Tree Combine Strings

Created By: Pranav Narayanan

/ Version: 2025.2.0

Create a public class TreeCombineStrings that provides a single class method named combineStrings. combineStrings accepts a single BinaryTree<String>. If the passed tree is null, throw an IllegalArgumentException. Otherwise, return the String represented by this tree.

For example, given the tree:

      "12"
     /    \
  "c"      "4"
     \
     "s"

You would return "cs124", by concatenating the left subtree "cs", the current node "12", and the right subtree "4". You may need to write a private helper method to solve this problem.

For reference, cs125.trees.BinaryTree has the following public properties: