Write a method named toString that returns a string representation of a binary tree of integers.
Your method accepts as its parameter a TreeNode that refers to the root of the tree.
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.
- A string representation of the right subtree.
For example, if a variable named tree refers to the root of the following tree:
(2 (8 (0)) (1 (7 (4)) (6 / (9))))
Then the call toString(tree) should return the following string:
"(2, (8, 0, empty), (1, (7, 4, empty), (6, empty, 9)))"
The quotes above are used to indicate that this is a string but should not be included in the string you return.
Assume that you are interacting with TreeNodes as defined below:
public class TreeNode {
public int data;
public TreeNode left;
public TreeNode right;
public TreeNode() { ... }
public TreeNode(int data) { ... }
public TreeNode(int data, TreeNode left, TreeNode right) { ... }
}
