Leetcode•Jun 29, 2025
Most Frequent Subtree Sum
Hazrat Ali
Leetcode
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]
Solution
/**
* @param {TreeNode} root
* @return {number[]}
*/
const findFrequentTreeSum = root => {
if (!root) {
return [];
}
const mapSum = {};
const mapCount = {};
let max = 0;
const helper = node => {
if (!node) {
return 0;
}
const left = helper(node.left);
const right = helper(node.right);
const sum = left + node.val + right;
const count = ~~mapSum[sum] + 1;
max = Math.max(max, count);
mapSum[sum] = count;
if (!mapCount[count]) {
mapCount[count] = new Set();
}
mapCount[count].add(sum);
return sum;
};
helper(root);
return [...mapCount[max]];
};