第四章的增补习题
----
4.1
-----
       A
   B     D
C      E   F

4.2
----

D和F
4.3
-----
template<class T>
Node*  build_tree(T* pre_order,T* mid_order，int n)//函数return当前子树的根节点
{
    TreeNode* root = NULL;
    if(n>=1)
    {
    TreeNode* root=new TreeNode(pre_order[0]);
 int m= find(pre_order,mid_order);//在中序遍历的表中找到子树的root,返回下标
        
 root->set_left(build_tree(pre_order+1,mid_order，m));
 root->set_right(build_tree(pre_order+1+n,mid_order,n-m-1));
    }
 return root;
//肯定有问题。大概是这样
}
4.4
----
template<class T>
void ancient(BinaryNode* root, T key)
{
    BinaryNode* pointer;
   while(root != NULL)
   {
       if(root->value() == key)
       {
           pointer = root;
    break;
       }
        ancient(root->leftchild());
        ancient(root->rightchild());
   }
   while(pointer != root)
   {
 cout<<pointer->value();
 pointer = parent(pointer);
   }
}
4.5
=====
大家来补齐

4.6
===
靠大家了

4.8
=====