【模板】并查集 两种路径压缩写法

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];
}*/ // 实践更好
if(p != parent[p])      //理论更好
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]++ ;
}
}
};