并查集

int FindSet(int x){

    int px = x;

    while(px != p[px])//当px不是树根，就一直往上冒

        px = p[px];

    while(x != px){//做一点优化，把路径上的结点的父结点全部设为根

        int temp = p[x];

        p[x] = px;

        x = temp;

    }

    return px;

}

void UnionSet(int x, int y){

    x = FindSet(x);

    y = FindSet(y);

    if(Rank[x] > Rank[y])

        p[y] = x;

    else{

        p[x] = y;

        if(Rank[x] == Rank[y])

            Rank[y]++;

    }

}