[Java] Find depth of binary tree

Here is a simple method to find the depth of a given binary tree, no matter if it's balanced or not.

The null tree has depth -1, the root has depth 0 and so on. By looking at the depth it is immediately possible to get the max number of elements at that depth: 2^depth.

You can check the code on my Gist (getTreeDepth) along with some test cases:

 //find depth of the tree  
   public static int getTreeDepth(BST root){  
     if(root == null) return -1;  
   
     return Math.max(getTreeDepth(root.left), getTreeDepth(root.right)) + 1;  
   }