class UnionFind{
private:
    int* parent;
    int* rank;
    int count;
public:
    UnionFind(int count){
        parent = new int[count];
        rank = new int[count];
        this->count = count;
        for(int i = 0;i < count; i++){
            parent[i] = i;
            rank[i] = 1;
        }
    }
    
 
~UnionFind(){
        delete[] parent;
        delete[] rank;
    }

    int find(int p){
        assert(p >= 0&&p < count);
 /*       while(parent[p] != p){
            parent[p] = parent[parent[p]];
            p = parent[p];
        }*/ // 實踐更好
        if(p != parent[p])      //理論更好
            parent[p] = find(parent[p]);
        
 
return parent[p];
    }

    bool isConnected(int p,int q){
        return find(p) == find(q);
    }

    void unionElements(int p,int q){
        int pRoot = find(p);
        int qRoot = find(q);
        if(pRoot == qRoot)
            return;


        if(rank[pRoot]  < rank[qRoot]){
            parent[pRoot] 
 
= qRoot;
        }else if(rank[pRoot] > rank[qRoot]){
            parent[qRoot] = pRoot;
        }else{
            parent[pRoot] = qRoot;
            rank[qRoot]++ ;
        }
    }
};

【模板】並查集 兩種路徑壓縮寫法