Find the size of the Binary Tree

Given a binary tree, write a method to return its size. The size of a tree is the number of nodes it contains.

Examples: 
     1                
    / \             
   2   3     ==>  7
  / \ / \           
 4  5 6  7

Need a hand? Try out these hints, one at a time.

Traverse each node of the tree recursively and increment a count variable for each node visited.

1. If root is null, return 0.

2. If root is not null, return size(root.left)+1+size(root.right)

public int size(TreeNode root) {
                              




    
}

Java

Python