二叉树创建
用下面的递归算法来创建一棵树：
btree* create_tree()
{
int value = 0;
scanf("%d", &value);
if(value==0)//输入零，表示左或右子树为空
{
return NULL;
}
btree *t = (btree *)malloc(sizeof(btree));
if(t==NULL)
{
return NULL;
}
memset(t,0,sizeof(btree));
t->value = value;
//递归创建左右子树：
printf("Please create the left tree of %d\n",value);
t->left = create_tree();
printf("Please create the right tree of %d\n",value);
t->right = create_tree();
return t;
}
