Binary Tree in Java without using add method

Question

I've been trying to switch over to Java from Node and one thing I'm wondering about is how to construct a Binary Tree without putting a sorting algorithm in. In Node, I could simply type the following:

function TreeNode(val) {
    this.val = val;
    this.left = this.right = null;
}
let tree = new TreeNode(4);
tree.left = new TreeNode(2);
tree.left.left = new TreeNode(1);

What is the Java equivalent to this? This is my current thought process

public class BinaryTree {
    private static TreeNode root;
    public static void main(String[] args) {
        BinaryTree bt = new BinaryTree();
        bt.TreeNode = ??

    }

  public class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode(int x) { val = x; }
  }

}

Possible duplicate of BinaryTree implementation in java

Shajal Ahamed
– Shajal Ahamed

2018-04-28 02:11:36 +00:00
Commented Apr 28, 2018 at 2:11 — Shajal Ahamed
– Shajal Ahamed, Commented Apr 28, 2018 at 2:11

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

@EJP: There is no need for two classes. Every tree node is a tree.

OP: Can you show me this with one class.

Based on the code https://stackoverflow.com/a/50072165/139985 ....

public class BinaryTree {
    int data;
    BinaryTree left, right;

    public BinaryTree(int data) {
        super();
        this.data = data;
        this.left = this.right = null; // redundant ...
    }

    public int height() {
        height(this);
    }

    private int height(BinaryTree node) {
        if (node == null) {
            return 0;
        }
        return Math.max(height(node.left), height(node.right)) + 1;
    }

    public static void main(String[] args) {
        BinaryTree tree = new BinaryTree(1);
        tree.left = new BinaryTree(2);
        tree.right = new BinaryTree(3);
        tree.left.right = new BinaryTree(4);

        System.out.println("The height of given binary tree is : " + tree.height());
    }

}

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Apr 28, 2018 at 2:50

Stephen C

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7 Comments

Shanu Gupta Over a year ago

Looks doable. I'm not sure how can I delete the root node (node 1) and make the root as some other node (say 4)?

Stephen C Over a year ago

By assignment. BinaryTree root = ...; root = newRoot; What we have here is an open data structure where operations are being performed by code outside of the abstraction boundary. With this kind of API, there is no clear need to distinguish root nodes. In fact, every node is a root node ... of a subtree.

Shanu Gupta Over a year ago

Looks fine to me. Depends on the requirements what design to choose.

Stephen C Over a year ago

Well yes. That applies to all data structures.

Shanu Gupta Over a year ago

This is the first time probably I'm seeing the Binary tree with one class. Everywhere I read, pople tends to have a separate Node class.

|

Shanu Gupta · Accepted Answer · 2018-04-28 02:41:27Z

0

You can structure your code something like this

class Node {
    int data;
    Node left, right;

    public Node(int data) {
        super();
        this.data = data;
        this.left = this.right = null;
    }

}

public class BinaryTree {
    Node root;

    public int height(Node node) {
        if (node == null)
            return 0;
        return Math.max(height(node.left), height(node.right)) + 1;
    }

    public static void main(String[] args) {
        BinaryTree tree = new BinaryTree();
        tree.root = new Node(1);
        tree.root.left = new Node(2);
        tree.root.right = new Node(3);
        tree.root.left.right = new Node(4);

        System.out.println("The height of given binary tree is : " + tree.height(tree.root));
    }

}

edited Apr 28, 2018 at 2:41

answered Apr 28, 2018 at 2:04

Shanu Gupta

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2 Comments

user207421 Over a year ago

There is no need for two classes. Every tree node is a tree.

user207421 Over a year ago

But still with two classes instead of one.

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