Description

Submission

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
    vector<TreeNode*> rets;
    unordered_map<string, int> key2id;
    unordered_map<int, int> id2cnt;
    int getId(TreeNode* root) {
        if(root == nullptr) return -1;

        string cur = to_string(root->val) + "#" + 
                    to_string(getId(root->left)) + "#" + 
                    to_string(getId(root->right));
        if(!key2id.count(cur)) key2id[cur] = key2id.size();

        if(++id2cnt[key2id[cur]] == 2) {
            rets.push_back(root);
        }

        return key2id[cur];
    }
public:
    vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
        getId(root);

        return rets;
    }
};