How to Print a Binary Tree Diagram in Java?

How do I print a binary tree in Java to visually represent its structure?

public class Node<A extends Comparable> {
    Node<A> left, right;
    A data;

    public Node(A data){
        this.data = data;
    }
}

To print a binary tree diagram in Java, we need to traverse the tree and format the output so that it resembles a graphical representation. This involves considering the layout of each node and its children in a way that visually depicts their relationships.

public class BinaryTreePrinter {

    public static <A> void printTree(Node<A> root) {
        int depth = getDepth(root);
        int maxWidth = (int) Math.pow(2, depth) - 1;
        String[][] output = new String[depth][maxWidth];

        for (int i = 0; i < depth; i++) {
            for (int j = 0; j < maxWidth; j++) {
                output[i][j] = " ";
            }
        }
        fillOutput(root, output, 0, 0, maxWidth);

        for (String[] line : output) {
            System.out.println(String.join("", line));
        }
    }

    private static <A> void fillOutput(Node<A> node, String[][] output, int row, int col, int width) {
        if (node != null) {
            output[row][col] = String.valueOf(node.data);
            fillOutput(node.left, output, row + 1, col - width / 4, width / 2);
            fillOutput(node.right, output, row + 1, col + width / 4, width / 2);
        }
    }

    private static <A> int getDepth(Node<A> node) {
        if (node == null) return 0;
        return 1 + Math.max(getDepth(node.left), getDepth(node.right));
    }
}

Causes

• Not using proper tree traversal methods.
• Failing to calculate node positions correctly for representation.
• Ignoring spacing and alignment of tree nodes.

Solutions

• Implement a recursive function to traverse the tree and collect node information.
• Use a formatting technique to display the nodes at appropriate levels.
• Utilize a queue to manage node positions for layout purposes.

Mistake: Not accounting for the depth of the tree when printing.

Solution: Use a recursive function to calculate and store the depth for proper formatting.

Mistake: Improper alignment of nodes leading to a jumbled output.

Solution: Adjust the spacing mechanism for each node based on its position and depth.