How to Solve Find Subtree Sizes After Changes Problem

You are given a tree rooted at node 0 that consists of n nodes numbered from 0 to n - 1. The tree is represented by an array parent of size n, where parent[i] is the parent of node i. Since node 0 is the root, parent[0] == -1. You are also given a string s of length n, where s[i] is the character assigned to node i. We make the following changes on the tree one time simultaneously for all nodes x from 1 to n - 1: Return an array answer of size n where answer[i] is the size of the subtree rooted at node i in the final tree.