求问并查集合并时随机合并+路径压缩期望复杂度

int fx[ 1000006 ];
int find(int x){
  return x == fx[ x ] ? x : fx[ x ] = find(fx[ x ]);
}
void merge(int x, int y){
  x = find(x), y = find(y);
  if(rand() & 1) swap(x, y);
  fx[ x ] = y;
}