Подскажите. Бинарное дерево

class Node
{
public:
String a;
int d;
Node* father;
Node* left;
Node* right;
Node(){father=left=right=0;}
};
 
class Tree
{
public:
Node* root;
Tree(){root=0;}
~Tree(){delete root;}
typedef Node* NodePtr;
void TreeInsert(String a);
void PreorderTree(Node* p, int l, ofstream &f);
Node* TreeSearch(Node* p, int d);
};
Tree T;
 
typedef Node* NodePtr;
 
void Tree::TreeInsert(String a)
{
int d =a[1]+a[2];
NodePtr z=new Node; z->d=d;
if(root==0) {root=z; return;}
NodePtr y;
NodePtr x=root;
while(x)
{y=x;
if(z->d<x->d) x=x->left;
else x=x->right;
}
z->father=y;
if (y->d>z->d)
y->left=z;
else y->right=z;
}
 
void Tree::PreorderTree(Node* p, int l, ofstream &f)
{
if(p)
{
for(int i=0; i<l; i++) f<<' ';
f<<p->d<<endl;
PreorderTree(p->left, l+1, f);
PreorderTree(p->right, l+1, f);
}
}
 
void __fastcall TForm1::Button1Click(TObject *Sender)
{
T.TreeInsert(Edit1->Text);
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::Button3Click(TObject *Sender)
{
ofstream f1("Tree.txt");
T.PreorderTree(T.root, 0, f1);
f1.close();
TreeView1->LoadFromFile("Tree.txt");
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button4Click(TObject *Sender)
{
Form1->Close();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Edit1MouseDown(TObject *Sender,
      TMouseButton Button, TShiftState Shift, int X, int Y)
{
Edit1->Clear();
}