Write a toString method for a binary tree of integers. The method should return "empty" for an empty tree. For a leaf node, it should return the data in the node as a string. For a branch node, it should return a parenthesized String that has three elements separated by commas: the data at the root, a string representation of the left subtree, and then a string representation of the right subtree. For example, if a variable t refers to reference tree #2, then the call t.toString() should return the following String (without the surrounding quotes):

"(2, (8, 0, empty), (1, (7, 4, empty), (6, empty, 9)))"

Transcribed Image Text:

Reference Tree #2 2 Reference Tree #1 1 7. 4 4 Reference Tree #3 2 3 8. 9. 3. 1.