利用二叉树写一个程序将算术表达式输入串（只要求1位整数）转换为后缀式，然后计算该表达式的值。要求： 1）从键盘或文件输入测试数据。 （2）输出算术表达式的后缀式和计算结果。

以下是利用二叉树实现算术表达式转换为后缀式的 Python 代码：

class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None

def is_operator(char):
    return char == '+' or char == '-' or char == '*' or char == '/'

def build_expression_tree(expression):
    stack = []
    for char in expression:
        if is_operator(char):
            right = stack.pop()
            left = stack.pop()
            node = TreeNode(char)
            node.left = left
            node.right = right
            stack.append(node)
        else:
            node = TreeNode(char)
            stack.append(node)
    return stack.pop()

def inorder_traversal(root, postfix):
    if root is None:
        return
    inorder_traversal(root.left, postfix)
    if is_operator(root.val):
        postfix.append(' ')
    postfix.append(root.val)
    if is_operator(root.val):
        postfix.append(' ')
    inorder_traversal(root.right, postfix)

def to_postfix(expression):
    root = build_expression_tree(expression)
    postfix = []
    inorder_traversal(root, postfix)
    return ''.join(postfix)

def calculate(expression):
    postfix = to_postfix(expression)
    stack = []
    for char in postfix:
        if char.isdigit():
            stack.append(int(char))
        elif char == '+':
            right = stack.pop()
            left = stack.pop()
            stack.append(left + right)
        elif char == '-':
            right = stack.pop()
            left = stack.pop()
            stack.append(left - right)
        elif char == '*':
            right = stack.pop()
            left = stack.pop()
            stack.append(left * right)
        elif char == '/':
            right = stack.pop()
            left = stack.pop()
            stack.append(left / right)
    return stack.pop()

接下来，我们可以使用该程序对测试数据进行测试，如下所示：

expression = input("请输入算术表达式：")
postfix = to_postfix(expression)
print("后缀式为：", postfix)
result = calculate(expression)
print("计算结果为：", result)

注意，该程序只能处理一位整数的算术表达式，如果需要处理多位整数，请在构建二叉树时适当修改代码。