C++ :

#include "stdio.h"
//程欣宇2014年4月13日
struct BinNode
{
	char data;
	BinNode *rchild;
	BinNode *lchild;
	BinNode(char d)
	{
		data=d;
		rchild=lchild=NULL;
	}
	~BinNode()
	{
		if (lchild) delete lchild;
		if (rchild) delete rchild;
	}
	static BinNode* create()
	{
		char ch;
		do{
			scanf("%c",&ch);
		}while(ch<=32);

		if (ch=='^')
			return NULL;
		BinNode *node=new BinNode(ch);
		node->lchild=create();
		node->rchild=create();
		return node;
	}
	void preTravel()
	{
		printf("%c",data);
		if (lchild) lchild->preTravel();
		if (rchild) rchild->preTravel();
	}
	void midTravel()
	{
		if (lchild) lchild->midTravel();
		printf("%c",data);
		if (rchild) rchild->midTravel();
	}
	void postTravel()
	{
		if (lchild) lchild->postTravel();
		if (rchild) rchild->postTravel();
		printf("%c",data);
	}
};

int main()
{
	BinNode *root;
	do{ 
		root=BinNode::create();
		if (root){
			root->preTravel();printf("\n");
			root->midTravel();printf("\n");
			root->postTravel();printf("\n");
			delete root;
		}
	}while(root); 
	return 0; 
}