0001 template <typename T> BNP<T> clone(BNP<T> p, BNP<T> t) { //深复制
0002    if (!t) return nullptr;
0003    BNP<T> x = new BinNode<T>(t->data, p, nullptr, nullptr, t->height, t->color); //先序
0004    x->lc = clone(x, t->lc);  x->rc = clone(x, t->rc);
0005    return x; //由t复制出x
0006 } //clone: p ~ Parent;  t ~ source Tree
0007 template <typename T> BinTree<T>& BinTree<T>::operator=(const BinTree<T>& t) { //赋值
0008    if (_root != t._root)
0009       { remove(_root);  _root = clone<T>(nullptr, t._root);  _size = t.size(); }
0010    return *this;
0011 } //operator=