Leetcode 3327. Check if DFS Strings Are Palindromes

Given a rooted tree with a character on each node, for every node i form the post-order DFS string obtained by recursively visiting its children in increasing index then appending the node's character, and return whether that string is a palindrome for each node. The core challenge is to decide this efficiently for all nodes (n up to 1e5) without rebuilding each traversal string from scratch.