leetcode 基本计算器 II python 之xue小的玩笑

class Solution(object):
    def calculate(self, s):
        return eval(s.replace('/','//'))

看来内置的执行效率还可以，哈哈哈

栈版本：

class Solution(object):
    def calculate(self, s):
        def add(x,y):
            return x+y
        def minus(x,y):
            return x-y
        def multiply(x,y):
            return x*y
        def divide(x,y):
            return x//y
        opes={'+':add,'-':minus,'*':multiply,'/':divide}
        sta_nums=[]
        sta_opes=[]
        numstr=''
        for si in s:
            if si==' ':
                continue
            if si>='0' and si<='9':
                numstr=numstr+si
                continue
            else:
                num=int(numstr)
                numstr=''
            if (len(sta_opes)>0 and sta_opes[-1] in [multiply,divide]):
                x=sta_nums.pop()
                ope=sta_opes.pop()
                num=ope(x,num)
            sta_nums.append(num)
            sta_opes.append(opes[si])
        num=int(numstr)
        if (len(sta_opes)>0 and sta_opes[-1] in [multiply,divide]):
            x=sta_nums.pop()
            ope=sta_opes.pop()
            num=ope(x,num)
        sta_nums.append(num)
        res=sta_nums.pop(0)
        while (len(sta_opes)>0):
            ope=sta_opes.pop(0)
            y=sta_nums.pop(0)
            res=ope(res,y)
        return res