508. Most Frequent Subtree Sum

[namespace-io]

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    unordered_map<int,int> m;
    int sumSubTree(TreeNode* root){
        if(root == nullptr) return 0;
        int left = sumSubTree(root->left);
        int right = sumSubTree(root->right);
        m[left + right + root->val] += 1;
        return left + right + root->val;
    }
    vector<int> findFrequentTreeSum(TreeNode* root) {
        sumSubTree(root);
        int MAX = 0;
        int ket = -1;
        vector<int> ret;
        for(auto p : m ){
            if(p.second > MAX){
                MAX = p.second;
                ret = vector<int>();
                ret.push_back(p.first);
            } else if(p.second == MAX){
                ret.push_back(p.first);
            }
        }
        
        return ret;
    }
};