class BSTreeNode: def init(self,data,lchild,rchild): self.data=data self.lchild=lchild self.rchild=rchild def InsertBST(root,data): if root==None: p=BSTreeNode(data,None,None) return p elif data<root.data : root.lchild=InsertBST(root.lchild,data) else: root.rchild=InsertBST(root.rchild,data) return root root=None valstr=list(map(int,input().split())) for i in range(0,len(valstr)): root=InsertBST(root,valstr[i]) 在以上程序中添加一个递减的排序的函数，使Input sample 10 5 3 4 15 20 12 output sample 20 15 12 10 5 4 3 Input sample 10 output sample 10 Input sample 20 10 output sample 20 10 Input sample 10 20 output sample 20 10

可以在已有的 `BSTreeNode` 类中添加一个递减排序的函数 `InOrderDescend(root)`，具体实现如下：

class BSTreeNode:
    def __init__(self, data, lchild, rchild):
        self.data = data
        self.lchild = lchild
        self.rchild = rchild
    
    def InsertBST(root, data):
        if root == None:
            p = BSTreeNode(data, None, None)
            return p
        elif data < root.data:
            root.lchild = InsertBST(root.lchild, data)
        else:
            root.rchild = InsertBST(root.rchild, data)
        return root
    
    def InOrderDescend(root):
        if root != None:
            InOrderDescend(root.rchild)
            print(root.data, end=' ')
            InOrderDescend(root.lchild)

然后在 `main` 函数中，先按照原来的代码构建出二叉搜索树，再调用 `InOrderDescend` 函数输出递减序列即可。完整代码如下：

class BSTreeNode:
    def __init__(self, data, lchild, rchild):
        self.data = data
        self.lchild = lchild
        self.rchild = rchild
    
    def InsertBST(root, data):
        if root == None:
            p = BSTreeNode(data, None, None)
            return p
        elif data < root.data:
            root.lchild = InsertBST(root.lchild, data)
        else:
            root.rchild = InsertBST(root.rchild, data)
        return root
    
    def InOrderDescend(root):
        if root != None:
            InOrderDescend(root.rchild)
            print(root.data, end=' ')
            InOrderDescend(root.lchild)

root = None
valstr = list(map(int, input().split()))
for i in range(0, len(valstr)):
    root = BSTreeNode.InsertBST(root, valstr[i])

BSTreeNode.InOrderDescend(root)