Problem URL: Maximum product of splitted binary tree

We will calculate the sum of all nodes in the tree and then we will calculate the sum of all nodes in the left and right subtrees. The answer will be the maximum of the product of the sum of the left and right subtrees and the product of the sum of the left and right subtrees and the sum of the rest of the nodes in the tree.

class Solution:
    def maxProduct(self, root: TreeNode) -> int:
        def getSum(root: Optional[TreeNode]) -> int:
            if not root:
                return 0
            return root.val + getSum(root.left) + getSum(root.right)

        self.sum = getSum(root)
        self.res = -1

        def dfs(root: Optional[TreeNode]) -> int:
            if not root:
                return 0
            left = dfs(root.left)
            right = dfs(root.right)

            val = root.val + left + right
            multiplication = (self.sum-val)*val
            self.res = max(self.res, multiplication)

            return val

        dfs(root)
        return self.res % (10**9+7)

Time complexity: O(n)
Space complexity: O(n)