How to Print a Binary Tree in Hierarchical Form in Java?

Print Hierarchical Binary Tree in Java

To print a binary tree, showing its hierarchical structure in a text representation, you can utilize the Builder pattern. This pattern allows you to construct a tree-like output incrementally.

One approach is to create a custom TreeNode class that represents each node in the tree:

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

To print the tree, you can use a recursive helper function that builds up a string representation of the tree:

public String toString() {
    StringBuilder builder = new StringBuilder();
    print(builder, "", "");
    return builder.toString();
}

private void print(StringBuilder builder, String prefix, String childrenPrefix) {
    builder.append(prefix).append(data).append('\n');
    if (left != null) {
        left.print(builder, childrenPrefix + "├── ", childrenPrefix + "│   ");
    }
    if (right != null) {
        right.print(builder, childrenPrefix + "└── ", childrenPrefix + "    ");
    }
}

Here, prefix represents the prefix for the current node, and childrenPrefix represents the prefix for its children. The function recursively prints each child with an appropriate prefix indentation.

By calling toString() on the root node, you can obtain a hierarchical representation of the entire tree:

TreeNode<Integer> root = new TreeNode<>(4);
root.left = new TreeNode<>(2);
root.right = new TreeNode<>(5);
System.out.println(root.toString());

This will output:

4
├── 2
└── 5

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