<p>Given the <code>root</code> of a binary tree, return <em>the number of nodes where the value of the node is equal to the <strong>average</strong> of the values in its <strong>subtree</strong></em>.</p>

<p><strong>Note:</strong></p>

<ul>
	<li>The <strong>average</strong> of <code>n</code> elements is the <strong>sum</strong> of the <code>n</code> elements divided by <code>n</code> and <strong>rounded down</strong> to the nearest integer.</li>
	<li>A <strong>subtree</strong> of <code>root</code> is a tree consisting of <code>root</code> and all of its descendants.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img src="https://assets.leetcode.com/uploads/2022/03/15/image-20220315203925-1.png" style="width: 300px; height: 212px;" />
<pre>
<strong>Input:</strong> root = [4,8,5,0,1,null,6]
<strong>Output:</strong> 5
<strong>Explanation:</strong> 
For the node with value 4: The average of its subtree is (4 + 8 + 5 + 0 + 1 + 6) / 6 = 24 / 6 = 4.
For the node with value 5: The average of its subtree is (5 + 6) / 2 = 11 / 2 = 5.
For the node with value 0: The average of its subtree is 0 / 1 = 0.
For the node with value 1: The average of its subtree is 1 / 1 = 1.
For the node with value 6: The average of its subtree is 6 / 1 = 6.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img src="https://assets.leetcode.com/uploads/2022/03/26/image-20220326133920-1.png" style="width: 80px; height: 76px;" />
<pre>
<strong>Input:</strong> root = [1]
<strong>Output:</strong> 1
<strong>Explanation:</strong> For the node with value 1: The average of its subtree is 1 / 1 = 1.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 1000]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 1000</code></li>
</ul>

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def averageOfSubtree(self, root: TreeNode) -> int:
        count = 0

        def postorder(root):
            nonlocal count

            if not root:
                return [0,0]

            l = postorder(root.left)
            r = postorder(root.right)

            nodecount = l[1] + r[1] + 1
            nodesum = l[0] + r[0] + root.val

            if nodesum//nodecount == root.val:
                count+=1
            
            return [nodesum, nodecount]
        
        postorder(root)
        return count
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