Generic Recursive Find Depth of Binary Tree in Java

A binary tree is a tree data structure in which each node has at most two children, which are referred to as the left child and the right child.

Depth of a binary tree is defined as the maximum length of all paths.

If a binary tree has only one node, its depth is 1. Following sample binary tree can be used as a test input.

There is a detailed and helpful description also at this link. 

package interviewquestions;

class Node<T>
{
   private T data;
   private Node<T> left;
   private Node<T> right;
 
   Node( T pData, Node<T> pLeft, Node<T> pRight )
   {
     data = pData;
     left = pLeft;
     right = pRight;
   }
 
   public void setLeftChild( Node<T> pLeft ) {  left = pLeft; }  
   public void setRightChild( Node<T> pRight ) { right = pRight; } 
 
   public Node<T> getLeftChild() { return left; }
   public Node<T> getRightChild() { return right; }  
   public T getData() { return data; }

}

class BinaryTree<T>
{
   Node<T> root;
 
   public BinaryTree(){  root = null; } 
 
   public void setRootNode( Node<T> pRoot ) {  root = pRoot; }
 
   public int depth() {
       return depth(root);
   }

   private int depth(Node<T> pNode) {
  
     if (pNode == null)
         return 0;

     int left = depth(pNode.getLeftChild());
     int right = depth(pNode.getRightChild());
       
     int result = (left>right) ? (left+1) : (right+1);
     return result;
   }
  
}

public class BinaryTreeOperations {
 
 public static void main(String[] args) {
  
    Node<Integer> node1 = new Node<Integer>( 1, null, null );
    Node<Integer> node2 = new Node<Integer>( 2, null, null );
    Node<Integer> node3 = new Node<Integer>( 3, null, null );
    Node<Integer> node4 = new Node<Integer>( 4, null, null );
    Node<Integer> node5 = new Node<Integer>( 5, null, null );
    Node<Integer> node6 = new Node<Integer>( 6, null, null );
  
    node1.setLeftChild(node2);
    node1.setRightChild(node3);
  
    node2.setLeftChild(node4);
    node2.setRightChild(node5);
  
    node3.setRightChild(node6);
  
    BinaryTree<Integer> binaryTree = new BinaryTree<Integer>();
    binaryTree.setRootNode(node1);
  
    System.out.println("Depth of Binary Tree = "+binaryTree.depth()); 
 }

}

Create a BinaryTreeOperations.java file in your workspace.

When the main method inside the BinaryTreeOperations class executed it is going to print :

Depth of Binary Tree = 3