二叉树的建立，遍历以及销毁

#include <iostream>  
#include <string>

using namespace std;  
  
struct node
{
	char da;
	node *lchild;
	node *rchild;
	
};
//前序遍历
void preorder(node* &re)
{
	if(re==NULL)
	{
		return;
	}
	cout<<re->da;
	preorder(re->lchild);
	preorder(re->rchild);
}
//中序遍历
void midorder(node* &mi)
{
	if(mi==NULL)
	{
		return;
	}
	midorder(mi->lchild);
	cout<<mi->da;
	midorder(mi->rchild);
}
//后序遍历
void postorder(node* &po)
{
	if(po==NULL)
	{
		return;
	}
	postorder(po->lchild);
	postorder(po->rchild);
	cout<<po->da;
}
//树的构建，先序创建
void createtree(node* &tt)
{
	char data;
	cin>>data;
	if(data=='#')
	{
		tt=NULL;
	}
	else
	{
		tt=new node;
		tt->da=data;
		createtree(tt->lchild);
		createtree(tt->rchild);
	}
}
//树的销毁,后序删除
void deletetree(node* &tt)
{
	if(tt==NULL)
	{
		return ;
	}
	deletetree(tt->lchild);
	deletetree(tt->rchild);
	delete tt;
}

int main()
{
	node  *head;
	
	createtree(head);
	preorder(head);
	midorder(head);
	postorder(head);
	deletetree(head);
	return 0;
}