树的删除操作

#include <stdio.h>

class Node
{
public:
Node * left;
Node * right;
Node * pre;
int data;
Node(int d,Node* p=NULL):data(d),left(0),right(0),pre(p)
{}
};

void insert(Node* head,int a)
{
if(head->data > a)
{
if(head->left==NULL) head->left=new Node(a,head);
else insert(head->left,a);
}else
{
if(head->right==NULL) head->right=new Node(a,head);
else insert(head->right,a);
}
}
void preorder_print(Node* d)
{
if(!d) return;
preorder_print(d->left);
printf("%d ",d->data);
preorder_print(d->right);
}
void transplant(Node* d,Node *u,Node *r)
{
if(u->pre==NULL){
*d=*r;
delete r;
}
else if(u->pre->left==u)
u->pre->left=r;
else
u->pre->right=r;
if(r)
r->pre=u->pre;
delete u;
}
//find minnum node
Node* minnum_node(Node* d)
{
if(d->left==NULL) return d;
return minnum_node(d->left);
}
//delete the first where data equals 'num'
void delete_node(Node* root,Node* d,int num)
{
if(d->data==num)
{
if(d->left==NULL) transplant(root,d,d->right);
else if(d->right==NULL) transplant(root,d,d->left);
else
{
auto min=minnum_node(d->right);
if(min->pre!=d)
transplant(root,min,min->right);
transplant(root,d,min);
min->pre=d->pre;
min->right=d->right;
min->right->pre=min;
min->left=d->left;
min->left->pre=min;
delete d;
}
}
else if(d->data>num) delete_node(root,d->left,num);
else delete_node(root,d->right,num);
}
void release(Node* d)
{
if(d->left!=NULL) release(d->left);
if(d->right!=NULL) release(d->right);
delete d;
}
int main()
{
Node* head=new Node(5);
int data[]={1,6,2,4,7,9,10,3};
for(int i=0;i<sizeof(data)/sizeof(int);++i)
insert(head,data[i]);
preorder_print(head);
putchar('\n');
delete_node(head,head,3);
preorder_print(head);
putchar('\n');
release(head);
return 0;
}