Printing Java Binary search tree

Question

How to print out a binary search tree in java? I have written the code to insert to the tree but without being able to print the tree i am insure if the elements are adding. I will post my code below.

public class TreeNode {

    TreeNode left;
    TreeNode right;
    TreeNode root;

    int data;

    public TreeNode(int d) {

        data = d;
        left = right = null;
        root = null;

    }

    public synchronized void insert(int d) {
        if (root == null){
            root = new TreeNode( d );
        }
        if (d < data) {
            if (left == null) {
                left = new TreeNode(d);
            } else {
                left.insert(d);
            }
        } else if (d > data) {
            if (right == null) {
                right = new TreeNode(d);
            } else {
                right.insert(d);
            }
        }
    }

    public TreeNode treeSearch(TreeNode root, int target) {
        if (root != null) {
            if (target < root.data) {
                root = treeSearch(root.left, target);
            } else if (target > root.data) {
                root = treeSearch(root.right, target);
            }
        }
        return root;
    }
}

there are at least too many ways of printing it. Can you provide a simple input and desired output? Have you tried anything yourself? — Fureeish
– Fureeish, Commented Nov 27, 2017 at 11:38
Its hard to explain the way i would like it but i will try. The output should output the root first then the lower level with the outputs branching off the root and then a lower level branching off this etc depending on the values inserted. — Bryan
– Bryan, Commented Nov 27, 2017 at 11:44
I think you missed the "Can you provide a simple input and desired output?" part while reading my comment. This meant editing the question, so everybody can easily see that, without looking at the comments — Fureeish
– Fureeish, Commented Nov 27, 2017 at 11:55
@Bryan I think you mean the Preorder traversal. For more info : geeksforgeeks.org/… — Jitin Kodian
– Jitin Kodian, Commented Nov 27, 2017 at 11:57

cse · Accepted Answer · 2017-11-28 06:33:24Z

4

You may use following method:

 void printTree(TreeNode node, String prefix)
 {
    if(node == null) return;

    System.out.println(prefix + " + " + node.data);
    printTree(node.left , prefix + " ");
    printTree(node.right , prefix + " ");
 }

Initial call should be printTree( root,""); from where you want to print the tree. Here root is reference of root node.

UPDATED:
You can see this code working here

edited Nov 28, 2017 at 6:33

answered Nov 27, 2017 at 11:51

cse

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12 Comments

Bryan Over a year ago

Thank you for your help, can you please explain this method in more detail.

cse Over a year ago

@Bryan This method use recursion-method to print the tree. First parameter is the node which is going to be printed and second argument is a String having spaces for better visibility of tree. This method returns if node is null. if it is not null then it prints data part and call itself for left and right child.

Bryan Over a year ago

Thank you for further explanation!

Bryan Over a year ago

your method has not solved it exactly but it has given me a basis to try modify and tweak it to what i want exactly!

cse Over a year ago

@Bryan What is not covered in this answer?

|

Shakhawat Hossain · Accepted Answer · 2017-11-27 11:54:02Z

0

you can print the tree data like this.

public void printTree(TreeNode root) {
        if (root == null) return;
        System.out.println(root.data);
        printTree(root.left);
        printTree(root.right);
    }

answered Nov 27, 2017 at 11:54

Shakhawat Hossain

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Comments

Joop Eggen · Accepted Answer · 2017-11-27 11:57:53Z

0

private void print(PrintWriter out) {
    print(root, out, "");
}

private void print(TreeNode subtree, PrintWriter out, String indent) {
    if (subtree != null) {
        print(subtree.left, out, indent + "--");
        out.printf("%s %s%n", indent, subtree.data);
        print(subtree.right, out, indent + "--");
    }
}

answered Nov 27, 2017 at 11:57

Joop Eggen

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Comments

Nazareth Keshishian · Accepted Answer · 2018-10-26 16:26:35Z

0

Infix order: Left - root - right

public String printInfix(TreeNode root) {//prints all the words in the tree in infix order
    if(root==null) {
        return "";
    }

     return printAll(root.left+" "+root.data+" "+printAll(root.right);
}

answered Oct 26, 2018 at 16:26

Nazareth Keshishian

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Comments

ani · Accepted Answer · 2023-05-07 23:13:05Z

0

public static void printTree(TreeNode node, String prefix)
    {
        if(node == null) return;

        printTree(node.right , prefix + "   ");
        System.out.println(prefix + node.data);
        printTree(node.left , prefix + "   ");
       
    }

Prints the tree in BST structure flatly

answered May 7, 2023 at 23:13

ani

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