void merge(int a, int b) {
  f[Find(a)] = Find(b);
}

int Find(int x) {
  return x == f[x] ? x : f[x] = Find(f[x]);
}

int pa = Find(a);
int pb = Find(b);
if(){
    s[pb] += s[pa]
}

int n, p[N], s[N], d[N];
//p[x] x的父亲节点  d[x] x到父节点的距离   s[x] 集合的大小
int Find(int x) { //距离查找
  if (p[x] != x) {
    int root = Find(p[x]);
    d[x] += d[p[x]];
    p[x] = root;
  }
  return p[x];
}
int pa = Find(a);
int pb = Find(b);
if () { //距离更新
  p[pa] = pb;
  d[pa] = s[pb];
  s[pb] += s[pa];
}