How to Print Binary Tree Diagrams in Java?

Printing Binary Tree Diagrams in Java

Introduction:

Visualizing the structure of a binary tree is crucial for facilitating understanding and debugging. This article examines a Java solution for printing binary trees in a diagrammatic format, providing a clear representation of the tree's structure.

Solution:

The primary goal of this solution is to print a binary tree by lines, similar to the following example:

4
/ \
2   5

For this purpose, the code provided establishes a custom Node class:

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

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

Printing by Lines:

The key insight of this solution is to print the tree in a top-down manner, line by line. Each node's children are printed on subsequent lines, with appropriate indents to indicate their level in the tree.

For example, to visualize a tree with the following structure:

        4
       / \
      2   5
    / \    /
   1   3  6

The output would resemble the following:

4
├── 2
│   ├── 1
│   └── 3
└── 5
   └── 6

Code Implementation:

The core logic is encapsulated in the print method of the TreeNode class:

public void print(StringBuilder buffer, String prefix, String childrenPrefix) {
    buffer.append(prefix);
    buffer.append(name);
    buffer.append('\n');
    for (Iterator<TreeNode> it = children.iterator(); it.hasNext();) {
        TreeNode next = it.next();
        if (it.hasNext()) {
            next.print(buffer, childrenPrefix + "├── ", childrenPrefix + "│   ");
        } else {
            next.print(buffer, childrenPrefix + "└── ", childrenPrefix + "    ");
        }
    }
}

This method recursively traverses the tree, printing line-by-line and accounting for appropriate indents to delineate the tree's structure.

Note:

While this solution focuses on printing arbitrary trees, it can be easily modified to specifically target binary trees by restricting each node to have a maximum of two children.

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