Maximum Product of Splitted Binary Tree

import { TreeNode } from '@algorithm/lib';
 
export function maxProduct(root: TreeNode | null): number {
  const MOD = 10 ** 9 + 7;
  if (root === null) {
    return 0;
  }
 
  let answer = 0;
  const totalValue = getTotalValue(root);
 
  function findMaxProduct(root: TreeNode | null): number {
    if (root === null) {
      return 0;
    }
 
    const leftTotalValue = findMaxProduct(root.left);
    const rightTotalValue = findMaxProduct(root.right);
    answer = Math.max(
      answer,
      (totalValue - leftTotalValue) * leftTotalValue,
      (totalValue - rightTotalValue) * rightTotalValue,
    );
    return root.val + leftTotalValue + rightTotalValue;
  }
  findMaxProduct(root);
 
  return answer % MOD;
}
 
function getTotalValue(root: TreeNode | null): number {
  if (root === null) {
    return 0;
  }
  return root.val + getTotalValue(root.left) + getTotalValue(root.right);
}