题目描述

代码实现

# coding:utf-8
# 仿LISP运算
# https://www.nowcoder.com/discuss/360006188531032064?sourceSSR=search
import sys

try:
    while True:
        line = sys.stdin.readline().replace('(', '( ').replace(')', ' )').strip().split(' ')
        if line == '':
            break
        stack = []
        op = []
        error_flag = False


        def cal(operation, p1, p2):
            res = 0
            if operation == 'add':
                res = p1 + p2
            if operation == 'sub':
                res = p1 - p2
            if operation == 'mul':
                res = p1 * p2
            if operation == 'div':
                if p2 == 0:
                    global error_flag
                    error_flag = True
                else:
                    res = p1 // p2
            return res


        for i in range(len(line)):
            if line[i] == '(':
                stack.append(line[i])
            elif line[i] == ')':
                if not stack:
                    error_flag = True
                    break
                stack.pop()
                p2 = int(op.pop())
                p1 = int(op.pop())
                operation = op.pop()
                res = cal(operation, p1, p2)
                op.append(res)
            else:
                op.append(line[i])
            if error_flag:
                break
        if error_flag:
            print("error")
        else:
            print(res)

except:
    print('error')