508. Most Frequent Subtree Sum

Given the root of a binary tree, return the most frequent subtree sum. If there is a tie, return all the values with the highest frequency in any order. The subtree sum of a node is defined as the sum of all the node values formed by the subtree rooted at that node (including the node itself). Example 1: Input: root = [5,2,-3] Output: [2,-3,4] Example 2: Input: root = [5,2,-5] Output: [2]