Untitled

class Solution {
    private long totalSum = 0;
    private long maxProduct = 0;
    private static final int MOD = 1_000_000_007;

    public int maxProduct(TreeNode root) {
        // Step 1: Calculate the total sum of the tree
        totalSum = calculateTotalSum(root);

        // Step 2: Calculate the maximum product by splitting the tree
        calculateSubtreeSum(root);

        // Step 3: Return the result modulo MOD
        return (int) (maxProduct % MOD);
    }

    private long calculateTotalSum(TreeNode node) {
        if (node == null) {
            return 0;
        }
        return node.val + calculateTotalSum(node.left) + calculateTotalSum(node.right);
    }

    private long calculateSubtreeSum(TreeNode node) {
        if (node == null) {
            return 0;
        }

        // Calculate the sum of the current subtree
        long subtreeSum = node.val + calculateSubtreeSum(node.left) + calculateSubtreeSum(node.right);

        // Calculate the product of splitting at this subtree
        long product = subtreeSum * (totalSum - subtreeSum);

        // Update the maximum product
        maxProduct = Math.max(maxProduct, product);

        return subtreeSum;
    }

    
}