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Copy path652. Find Duplicate Subtrees.cpp
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652. Find Duplicate Subtrees.cpp
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/**
* 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 {
public:
vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
unordered_map<string,pair<int,int>> hash;
vector<TreeNode*> res;
dfs(root,hash,res);
return res;
}
int dfs(TreeNode* root, unordered_map<string,pair<int,int>> &hash, vector<TreeNode*> &res) {
if (!root) return 0;
string s = to_string(root->val) + "," + to_string(dfs(root->left, hash, res)) + "," + to_string(dfs(root->right, hash, res));
if (hash.find(s) == hash.end()) {
hash[s] = {nextID,1};
nextID++;
}
else if (++hash[s].second == 2) {
res.push_back(root);
}
return hash[s].first;
}
private:
int nextID = 1;
};