hdu3487 Play with Chain

维护无序序列。结点信息包括flip和s。

cut操作：

void cut(int a, int b, int c) {
  Node *left, *mid, *right, *o;
  split(ss.root, a, left, o);
  split(o, b-a+1, mid, right);
  ss.root = merge(left, right);

  split(ss.root, c+1, left, right);
  ss.root = merge(merge(left, mid), right);
}