Write a program that reads an expression in a line as input and prints out the result. Only integers and operators below are allowed in the expression: + - * / % ( ) 输入格式: A line of expression. 输出格式: The result.

好的，我可以为您提供一个基于 Python 的解决方案。请注意，此程序仅适用于输入格式符合要求的表达式。

# 定义算术运算函数
def arithmetic(op, a, b):
    if op == '+':
        return a + b
    elif op == '-':
        return a - b
    elif op == '*':
        return a * b
    elif op == '/':
        return a / b
    elif op == '%':
        return a % b

# 定义运算符优先级
precedence = {'+': 1, '-': 1, '*': 2, '/': 2, '%': 2}

# 定义中缀表达式转后缀表达式函数
def infix_to_postfix(expr):
    stack = []
    postfix = []
    for token in expr:
        if token.isdigit():
            postfix.append(token)
        elif token in precedence:
            while stack and stack[-1] != '(' and precedence[token] <= precedence[stack[-1]]:
                postfix.append(stack.pop())
            stack.append(token)
        elif token == '(':
            stack.append(token)
        elif token == ')':
            while stack and stack[-1] != '(':
                postfix.append(stack.pop())
            stack.pop()
    while stack:
        postfix.append(stack.pop())
    return postfix

# 定义计算后缀表达式函数
def evaluate_postfix(expr):
    stack = []
    for token in expr:
        if token.isdigit():
            stack.append(int(token))
        elif token in precedence:
            b = stack.pop()
            a = stack.pop()
            stack.append(arithmetic(token, a, b))
    return stack.pop()

# 读取表达式并输出结果
expr = input().split()
postfix = infix_to_postfix(expr)
result = evaluate_postfix(postfix)
print(result)

您可以将上述代码复制粘贴到 Python 编辑器中，然后运行程序。程序将提示您输入表达式，并输出计算结果。例如，如果您输入 "2 + 3 * 4", 程序将输出 14。