2019-08-20剑指 把字符串转换成整数

20min

from functools import reduce
# -*- coding:utf-8 -*-
class Solution:
    def StrToInt(self, s):
        return reduce(lambda x,y:x*10+y,map(lambda x:int(x),s))  #reduce函数的妙用

class Solution2:
    def StrToInt(self, s):
        flag=0
        if not s :return 0
        elif s[0]=='-' or s[0]=='+':flag=1
        sum=0
        for i in range(flag,len(s)):
            if not s[i].isdigit():return 0  #isalnum，包括了字母
            sum=sum*10+int(s[i])
        return sum if s[0]!='-' else -sum


if __name__ == '__main__':
    t=Solution2()
    print(t.StrToInt('2147483647'))
    print(t.StrToInt('+2147483647'))
    print(t.StrToInt('-2147483647'))
    print(t.StrToInt('1a33'))
    print(t.StrToInt('a133'))