508 Most Frequent Subtree Sum

/**
 * 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:
    vector<int> findFrequentTreeSum(TreeNode* root) {
        map<int,int>tmp;//<SubTreeSum,count>
        vector<int>ans;
        findSum(root,tmp);//调用函数，记录每一个结点的SubTreeValue
        int max=0;
        for(auto p:tmp){//遍历map，max表示当前mostfrequent结点的次数
            if(max<p.second){
                ans.clear();//清空vector
                ans.push_back(p.first);
                max=p.second;
            }else if(max==p.second){
                ans.push_back(p.first);
            }
        }
        return ans;
    }
    int findSum(TreeNode* root,map<int,int>&tmp){
        if(root==NULL){
            return 0;
        }else{
            root->val+=findSum(root->left,tmp)+findSum(root->right,tmp);
            if(tmp.find(root->val)!=tmp.end()){
                tmp[root->val]++;//不是第一次出现++
            }else{
                tmp[root->val]=1;//第一次出现初始化为1
            }
            return root->val;
        }
        
    }
    
};