HeightOfBT.java

// Suppose we have a Node class that representing the node in the BT
// public class Node{
//     int val;
//     Node left;
//     Node right;
// }
public class HeightOfBT{
    private int height;
    public int getHeight(Node root){
        height = 0;
        traverse(root, 0);
        return height;
    }
    
    private void traverse(Node root, int level){
        if(root == null) return;
        
        if(level > height) height = level;
        traverse(root.left, level + 1);
        traverse(root.right, level + 1);
    }
}