508. Most Frequent Subtree Sum LeetCode Solution

In this guide, you will get 508. Most Frequent Subtree Sum LeetCode Solution with the best time and space complexity. The solution to Most Frequent Subtree Sum problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Problem Statement
Complexity Analysis
Most Frequent Subtree Sum solution in C++
Most Frequent Subtree Sum solution in Java
Most Frequent Subtree Sum solution in Python
Additional Resources

508. Most Frequent Subtree Sum LeetCode Solution image

Problem Statement of 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]

Constraints:

The number of nodes in the tree is in the range [1, 104].
-105 <= Node.val <= 105

Complexity Analysis

Time Complexity: O(n)
Space Complexity: O(n)

508. Most Frequent Subtree Sum LeetCode Solution in C++

class Solution {
 public:
  vector<int> findFrequentTreeSum(TreeNode* root) {
    vector<int> ans;
    unordered_map<int, int> count;
    int maxCount = 0;

    sumDownFrom(root, count);

    for (const auto& [_, freq] : count)
      maxCount = max(maxCount, freq);

    for (const auto& [sum, freq] : count)
      if (freq == maxCount)
        ans.push_back(sum);

    return ans;
  }

 private:
  int sumDownFrom(TreeNode* root, unordered_map<int, int>& count) {
    if (root == nullptr)
      return 0;

    const int sum = root->val + sumDownFrom(root->left, count) +
                    sumDownFrom(root->right, count);
    ++count[sum];
    return sum;
  }
};
/* code provided by PROGIEZ */

508. Most Frequent Subtree Sum LeetCode Solution in Java

class Solution {
  public int[] findFrequentTreeSum(TreeNode root) {
    List<Integer> ans = new ArrayList<>();
    Map<Integer, Integer> count = new HashMap<>();
    int maxCount = 0;

    sumDownFrom(root, count);

    for (final int freq : count.values())
      maxCount = Math.max(maxCount, freq);

    for (final int sum : count.keySet())
      if (count.get(sum) == maxCount)
        ans.add(sum);

    return ans.stream().mapToInt(Integer::intValue).toArray();
  }

  private int sumDownFrom(TreeNode root, Map<Integer, Integer> count) {
    if (root == null)
      return 0;

    final int sum = root.val + sumDownFrom(root.left, count) + sumDownFrom(root.right, count);
    count.merge(sum, 1, Integer::sum);
    return sum;
  }
}
// code provided by PROGIEZ

508. Most Frequent Subtree Sum LeetCode Solution in Python

class Solution:
  def findFrequentTreeSum(self, root: TreeNode | None) -> list[int]:
    if not root:
      return []

    count = collections.Counter()

    def dfs(root: TreeNode | None) -> int:
      if not root:
        return 0

      summ = root.val + dfs(root.left) + dfs(root.right)
      count[summ] += 1
      return summ

    dfs(root)
    maxFreq = max(count.values())
    return [summ for summ in count if count[summ] == maxFreq]
 # code by PROGIEZ