Leetcode 684. Redundant Connection 並查集 C++

class UnionFindSet {
public:
    UnionFindSet(int n){
        ranks_ = vector<int>(n+1,0);
        parents_ = vector<int>(n+1,0);
        
        for(int i=0; i<parents_.size(); i++)
            parents_[i]=i;
    }
    
    bool Union(int u, int v){
        int pu = Find(u);
        int pv = Find(v);
        if(pu==pv) return false;
        
        if(ranks_[pv] > ranks_[pu])
            parents_[pu] = pv;
        else if(ranks_[pu] > ranks_[pv])
            parents_[pv] = pu;
        else{
            parents_[pv] = pu;
            ranks_[pv] +=1;
        }
        return true;
    }

    int Find(int u){
        if(u!= parents_[u])
            parents_[u] = Find(parents_[u]);
        return parents_[u];
    }
        
private:
        vector<int> parents_;
        vector<int> ranks_;
};

class Solution {
public:
    vector<int> findRedundantConnection(vector<vector<int>>& edges) {
        UnionFindSet s(edges.size());
        
        for(const auto& edge: edges)
            if(!s.Union(edge[0], edge[1]))
                return edge;
        return {};
        
    }
};