問題： 計(jì)算字符串“10+12*13-30/20”的值

思路：

第一步：從左到右解析字符串，將數(shù)值與運(yùn)算符放入數(shù)組

第二步：先計(jì)算乘除法，將求值放入隊(duì)列

第三步：依次出隊(duì)列，計(jì)算最終值

python代碼實(shí)現(xiàn)如下：

#!/usr/bin/python # -*- coding: utf-8 -*- import sys cal_string = '10+12*13-30/20' #分隔字符串 symbol = ['+', '-', '*', '/'] one_word = '' data = [] for c in cal_string:if c not in symbol:one_word += celse:data.append(int(one_word))data.append(c)one_word = '' data.append(one_word) print data#計(jì)算乘除，將運(yùn)算完的值入隊(duì)列 hign_symbol = ['*', '/'] queue = [] cur_symbol = '' for one in data:if cur_symbol == '':if one in hign_symbol:cur_symbol = one else:queue.append(one)else:last_one = queue.pop()if cur_symbol == '*':new_one = float(last_one) * float(one) queue.append(new_one)else:new_one = float(last_one) / float(one)queue.append(new_one)cur_symbol = '' print queue#將隊(duì)列數(shù)據(jù)出隊(duì)列，計(jì)算最后值 result = 0 cur_symbol = '' for one in queue:if one != '+' and one != '-':if cur_symbol == '':result = oneelse:if cur_symbol == '+':result = result + oneelse:result = result - oneelse:cur_symbol = one print result 輸出結(jié)果：

[10, '+', 12, '*', 13, '-', 30, '/', '20'] [10, '+', 156.0, '-', 1.5] 164.5

總結(jié)

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