学步园

# include <stdio.h>
# include <stdlib.h>
struct treenode
{
	char ch;
	treenode *left,*right;     /*左指针和右指针*/
};
typedef treenode *treelink;
int main()
{
	treelink createtree(treelink);
	void preorder(treelink);
	void medorder(treelink);
	void postorder(treelink);

	treelink T=NULL;
	T=createtree(T);
	printf("先序遍历结果为：\n");
	preorder(T);
	putchar(10); 
	printf("中序遍历结果为：\n");
	medorder(T);
	putchar(10);
	printf("后序遍历结果为：\n");
	postorder(T);
	putchar(10);
	system("pause");
return 0;
}

treelink createtree(treelink T)  /*树的递归创建*/
{   
	char temp;
	scanf("%c",&temp);
	getchar();
	if(temp=='#')              
	{
		T=NULL;
	}
	else 
	{
		T=(treelink)malloc(sizeof(treenode));
		T->ch=temp;
		T->left=createtree(T->left);
		T->right=createtree(T->right);
	}
	return T;
}

void preorder(treelink T)     /*先序遍历*/
{
	if(!T)
		return;
	printf("%c\t",T->ch);
	preorder(T->left);
	preorder(T->right);
}

void medorder(treelink T)    /*中序遍历*/
{
if(!T)
	return ;
medorder(T->left);
printf("%c\t",T->ch);
medorder(T->right);
}

void postorder(treelink T)    /*后序遍历*/
{
if(!T)
	return ;
postorder(T->left);
postorder(T->right);
printf("%c\t",T->ch);
}

调用这个程序，输入为：

建立的树为：