/************************************************************************
* Create Date                   :2014/12/10
* Author                        :zhuang_569 
* Description                   :二叉树的创建
*************************************************************************/
#include "iostream"
using namespace std;
typedef char ELEM_TYPE;
typedef struct	BiTNode
	{
	    ELEM_TYPE	data;
	    struct BiTNode *lchild;
	    struct BiTNode *rchild;	
	}BiTNode,*pBiTNode;

//函数声明
pBiTNode CreateBeTree(void);
void PreOrderTraverse(pBiTNode pRoot);
void InOrderTraverse(pBiTNode pRoot);
void PostOrderTraverse(pBiTNode pRoot);
int main(void)
{
	pBiTNode pBeTreeRoot;
	pBeTreeRoot = CreateBeTree();	//创建二叉树根节点
	cout<<"二叉树先序输出：";
	PreOrderTraverse(pBeTreeRoot);
	cout<<"\n"<<"二叉树中序输出：";
	InOrderTraverse(pBeTreeRoot);
	cout<<"\n"<<"二叉树后序输出：";
	PostOrderTraverse(pBeTreeRoot);
	return 0;
}

//利用先序遍历建立二叉树
pBiTNode CreateBeTree(void)
{
	pBiTNode pRoot;			
	ELEM_TYPE ch;
	cin >> ch;	
	if('@' == ch)
	{
		pRoot = NULL;
	}
	else
	{
		pRoot = new BiTNode;	//为新的节点分配内存空间
		pRoot->data = ch;
		pRoot->lchild = CreateBeTree();
		pRoot->rchild = CreateBeTree();
	}
		return pRoot;			//返回根节点的地址
}

//先序遍历二叉树
void PreOrderTraverse(pBiTNode pRoot)
{
	if(NULL != pRoot)
	{
	 	cout << pRoot->data;
		PreOrderTraverse(pRoot->lchild);
		PreOrderTraverse(pRoot->rchild);
	}
}

//中序遍历二叉树
void InOrderTraverse(pBiTNode pRoot)
{
	if(NULL != pRoot)
	{
		InOrderTraverse(pRoot->lchild);
		cout << pRoot->data;
		InOrderTraverse(pRoot->rchild);
	}
}

//后序遍历二叉树
void PostOrderTraverse(pBiTNode pRoot)
{
	if(NULL != pRoot)
	{
		PostOrderTraverse(pRoot->lchild);
		PostOrderTraverse(pRoot->rchild);
		cout << pRoot->data;
	}
}

树：

测试结果：