How to display binary search tree rotated 90deg which starts from lowest point

Question

I have created a Binary Search Tree as follows:

static class TreeNode{
    private int data;
    private TreeNode leftChild;
    private TreeNode rightChild;

    public TreeNode(int data){
        this.data=data;
    }

    public void add(int data){
        if( data >= this.data){
            if(this.rightChild == null){
                this.rightChild = new TreeNode(data);
            }else{
                this.rightChild.add(data);
            }
        }else {
            if(this.leftChild == null){
                this.leftChild = new TreeNode(data);
            }else {
                this.leftChild.add(data);
            }
        }
    }

    public int getData(){
        return data;
    }
    public  void setLeftChild(TreeNode leftChild){
        this.leftChild = leftChild;
    }
    public  void setRightChild(TreeNode rightChild){
        this.rightChild = rightChild;
    }
    public TreeNode getLeftChild(){
        return leftChild;
    }
    public TreeNode getRightChild(){
        return rightChild;
    }
    public void print() {
        print("", this, false);
    }

    public void print(String prefix, TreeNode n, boolean isLeft) {
        if (n != null) {
            System.out.println (prefix + (isLeft ? "|-- " : "\\-- ") + n.data);
            print(prefix + (isLeft ? "|   " : "    "), n.leftChild, true);
            print(prefix + (isLeft ? "|   " : "    "), n.rightChild, false);
        }
    }
}

static class BinaryTree{

  private TreeNode root;

  public void pprint(){
      traversePreOrder(this.root);
  }

  public void traversePreOrder(TreeNode node) {
      if (node != null) {
          System.out.print(" " + node.data);
          traversePreOrder(node.leftChild);
          traversePreOrder(node.rightChild);
      }
  }
}

I want to display my tree, however not normally, but in rotated 90deg, which starts from the lowest point.

For example: if the input is: 901 292 247 997 457 468 216 82 530 524 793 952 730 764 820 460 424

The output should look like this:

Another Example: if the input is: 302 946 638 376 604 610 45 547 76 347 694 495 51 130 159

Output:

P.S I tried with the information in How to print binary tree diagram in Java, but I was unable to solve the issue :(

Answer 1

Some issues:

• You should not need to pass a node instance as argument when you already have the current (this) instance.

• pprint never calls the print method on the TreeNode class

• The print method on the TreeNode class visits the nodes in pre-order. For in-order, you should first visit the left subtree, then the node itself and then the right subtree

Here is a correction to the print methods in TreeNode:

class TreeNode{

    /* ... constructor and other methods here ... */

    public void print() {
        print("", "", "", "");
    }

    public void print(String prefix, String left, String mid, String right) {
        String indent = " ".repeat(String.valueOf(data).length());
        if (leftChild != null) {
            leftChild.print(prefix + left + indent, " ", "┌", "│");
        }
        System.out.println(prefix + mid + data 
                           + " ┐┘┤".charAt((leftChild  != null ? 2 : 0) 
                                         + (rightChild != null ? 1 : 0)));
        if (rightChild != null) {
            rightChild.print(prefix + right + indent, "│", "└", " ");
        }
    }
}

And in BinaryTree we would simply defer the job to the TreeNode class:

class BinaryTree {
    private TreeNode root;

    public void pprint() {
        if (root != null) {
            root.print();
        }
    }

    public void add(int data) {
        if (root == null) {
            root = new TreeNode(data);
        } else {
            root.add(data);
        }
    }
}