构建二叉树并实现递归遍历

执行程序时输入ABD#F##EG##H##C##

#include<iostream>
using namespace std;

typedef struct BinNode{
char data;
BinNode *lchild,*rchild;
}bin_tree,*tree;

void creat_tree(tree &t){
char ch;
cin>>ch;
if(!cin.eof()){
if(ch=='#')
t=NULL;
else{
t=new bin_tree;
if(!t)
exit(0);
t->data=ch;
creat_tree(t->lchild);
creat_tree(t->rchild);
}
}
}

void pre_order(tree &t){
if(t){
cout<<t->data<<"  ";
pre_order(t->lchild);
pre_order(t->rchild);
}
}

void mid_order(tree &t){
if(t){
mid_order(t->lchild);
cout<<t->data<<"  ";
mid_order(t->rchild);
}
}

void post_order(tree &t){
if(t){
post_order(t->lchild);
post_order(t->rchild);
cout<<t->data<<"  ";
}
}

void main(){
tree t;
cout<<"请输入二叉树节点：";
creat_tree(t);
cout<<"\n先序遍历序列为：";
pre_order(t);
cout<<"\n中序遍历序列为：";
mid_order(t);
cout<<"\n后序遍历序列为：";
post_order(t);
cout<<endl;
}