搜索二叉树

#include<stdio.h>

struct Node
{
    int key;
    Node *p;
    Node *left;
    Node *right;
    Node(int k = 0)
    {
        p=NULL;
        left=NULL;
        right=NULL;
        key=k;
    }
private:
    Node& operator=(const Node&);
}*NIL;

struct Tree
{
    Node *root;
    Tree()
    {
        root = NIL;
    }
};
//求最小值
Node* Minimum(Node *root)
{
    while(root->left != NIL)
    {
        root = root->left;
    }
    return root;
}
//中序遍历
void InorderTreeWalk(const Node *root)
{
    if(root != NIL)
    {
        InorderTreeWalk(root->left);
        printf("%d ",root->key);
        InorderTreeWalk(root->right);
    }
}
//查询
Node* TreeSearch(const Tree *T,const int k)
{
    Node *x=T->root;
    while(x != NIL && x->key!=k)
    {
        if(x->key>k)
        {
            x = x->left;
        }
        else
        {
            x = x->right;
        }
    }
    return x;
}
//插入
void TreeInsert(Tree *T, Node *z)
{
    Node *y = NIL;
    Node *x = T->root;
    while (x != NIL)
    {
        y=x;
        if(z->key < x->key)
        {
            x = x->left;
        }
        else
        {
            x = x->right;
        }
    }
    z->p = y;
    z->left = NIL;
    z->right = NIL;
    if(y == NIL)
    {
        T->root = z;
    }
    else
    {
        if(z->key < y->key)
        {
            y->left = z;
        }
        else
        {
            y->right = z;
        }
    }
}
//交换子树
void Transplant(Tree *T,Node *u,Node* v)
{
    if(u->p == NIL)
    {
        T->root = v;        
    }
    else
    {
        if(u == u->p->left)
        {
            u->p->left = v;
        }
        else
        {
            u->p->right = v;
        }
    }
    if(v != NIL)
    {
        v->p = u->p;
    }
}
//删除
void TreeDelete(Tree *T, Node *z)
{
    if(z->left == NIL)
    {
        Transplant(T,z,z->right);
    }
    else if(z->right == NIL)
    {
        Transplant(T,z,z->left);
    }
    else
    {
        Node *y = Minimum(z->right);
        if(y!=z->right)
        {
            Transplant(T,y,y->right);
            y->right = z->right;
            z->right->p = y;
        }
        Transplant(T,z,y);
        y->left = z->left;
        z->left->p = y;
    }
}

int main()
{
    Tree T;
    for(int i=10;i>9;i--)
    {
        TreeInsert(&T,new Node(i));
    }
    InorderTreeWalk(T.root);
    printf("\n");
    Node *temp;
    Node Temp;
    if((temp = TreeSearch(&T,5)) != NIL)
    {
        printf("find 5\n");
        TreeDelete(&T,temp);
        printf("Delete 5\n");
    }
    InorderTreeWalk(T.root);
    printf("\n");
    /*
    if(TreeSearch(&T,0) == NIL)
    {
        printf("do not find 0\n");
    }
    */
    return 0;
}