Write a method that receives the root of a binary tree and finds the count of all subtrees having the same value in all of its nodes.

For example: if the method receives the root of the following tree:

It will return $7$ because the following subtrees have the same value in all of its nodes:

Note: binary tree is constructed of nodes which are instances of the following class:

class BinaryTreeNode

$\{$

int data;

BinaryTreeNode leftchild $=$ null;

BinaryTreeNode rightchild $=$ null;

BinaryTreeNode$($int data$)\{$

this.data $=$ data;

$\}$

$\}$