难点创建二叉树，交换，这里均采用递归方法来做。

相信大家一看就懂。

// ChangeChild.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <stdlib.h>
#include <iostream>
#include <Windows.h>

using namespace std;

typedef char element;

typedef struct bitree
{
	element data;
	struct bitree* lchild;
	struct bitree* rchild;
}bitree;
//交换左右子树
void changechild(bitree* root)
{
	//element eleTemp;
	bitree* bitTemp;
	if (root == NULL)
	{
		root = NULL;
	}
	else
	{
		bitTemp = root->lchild;
		root->lchild = root->rchild;
		root->rchild = bitTemp;
		changechild(root->lchild);
		changechild(root->rchild);
	}
}
void CreateBiTree(bitree* &T)
{
	char  ch;
	cin>>ch;
	if(ch=='#') T=NULL;
	else
	{
		T=(bitree *)malloc(sizeof(bitree));
		T->data=ch;
		cout<<"put in \'"<<T->data<<"\' lchild"<<endl;
		CreateBiTree(T->lchild);
		cout<<"put in \'"<<T->data<<"\' rchild"<<endl;
		CreateBiTree(T->rchild);
	}
}//CreateBiTree
void PreTraversal(bitree* T)
{
	if (T == NULL)
	{
		return;
	}
	else
	{
		printf("%c,",T->data);
		PreTraversal(T->lchild);
		PreTraversal(T->rchild);
	}
}
int _tmain(int argc, _TCHAR* argv[])
{
	bitree* b1 ;
	b1= (bitree *)malloc(sizeof(bitree));
	bitree* 	broot;
	broot = b1;
	printf("enter # is over,put in root node\n");
	CreateBiTree(b1);
	printf("created tree\n");
	PreTraversal(b1);
	changechild(b1);
	printf("\nafter change lchild ,rchild\n");
	PreTraversal(b1);
	system("pause");
	return 0;
}