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class TNode {
public:
    int val;
    unordered_set<TNode*> neigh;
    TNode(int val) {
        this->val = val;    
    }
};

class Solution {
public:
    vector<int> findMinHeightTrees(int n, vector<pair<int, int>>& edges) {
        map<int, TNode*> val_node;
        for(int i = 0; i < n; i++) {
            TNode* tmp = new TNode(i);
            val_node[i] = tmp;
        }
        
        for(int i = 0; i < edges.size(); i++) {
            pair<int, int> pp = edges[i];
            val_node[pp.first]->neigh.insert(val_node[pp.second]);
            val_node[pp.second]->neigh.insert(val_node[pp.first]);
        }
        
        map<int, TNode*>::iterator m_iter;
        while(val_node.size() > 2) {
            list<TNode*> listg;
            for(m_iter = val_node.begin(); m_iter != val_node.end(); m_iter++) {
                if(m_iter->second->neigh.size() == 1) {
                    listg.push_back(m_iter->second);
                }
            }
            list<TNode*>::iterator l_iter;
            for(l_iter = listg.begin(); l_iter != listg.end(); l_iter++) {
                TNode* p = (*(*l_iter)->neigh.begin());
                p->neigh.erase(*l_iter);
                (*l_iter)->neigh.erase(p);
                val_node.erase((*l_iter)->val);
            }
        }
        vector<int> res;
        for(m_iter = val_node.begin(); m_iter != val_node.end(); m_iter++) {
            res.push_back(m_iter->first);
        }
        return res;
    }
};