Leetcode 3575. Maximum Good Subtree Score

For each node in a rooted tree, find the maximum sum of a subset of nodes in its subtree such that across the chosen nodes each decimal digit 0–9 appears at most once, then return the sum of all these per-node maxima modulo 1e9+7. The core challenge is a tree DP that merges children using 10-bit masks (2^10 states) representing used digits and discards nodes whose own value has repeated digits.