一、题目

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

 

二、解析

本题是指将字符串中的连续数字输出出来，需要考虑多种情况：

1>空字符串、无数字，返回0

2>前边多余空格，"    1234"，返回1234

3>有正负符号的，"   -234"，返回-234

4>有其他无效字符的，保留之前数字结果，"    -234&(90123"，返回-234

5>大于32bit范围，返回题目要求

 

三、代码

1 class Solution: 2     # @param {string} str 3     # @return {integer} 4     def myAtoi(self, s): 5         """ 6         1.null, return 0 7         2.not null: 8             1>white space 9             2>check + and -10             3>check other characters11             4>check range12         """13         #null14         if s == "":15             return 016     17         #remove white space.18         start = 019         while s[start] == " ":20             start += 121         s = s[start:]22         23         #check + and -24         minusCount = 025         if s[0] == "-":26             minusCount += 127             s = s[1:]28         elif s[0] == "+":29             s = s[1:]30         elif s[0] >= "0" and s[0] <= "9":31             pass32         else:33             return 034     35         #check other characters36         rst = ""37     38         for i in s:39             if i >= "0" and i <= "9":40                 rst += i41             else:42                 break43         if rst == "":44             return 045         46         #return results47         if minusCount % 2 == 0:48             if int(rst) <= 2147483647:49                 return int(rst)50             else:51                 return 214748364752         else:53             if int(rst) <= 2147483648:54                 return -int(rst)55             else:56                 return -2147483648

 

四、总结

1.下午做完，这个就熟练多了。

2.这题有个bug，但不算什么大问题。测试例“+-2”，返回结果是0.但是个人觉得应该返回-2.

3.晚安