Leetcode 8. String to Integer (atoi)

https://leetcode.com/problems/string-to-integer-atoi/

Title: Converts a string to an integer.

Rules:

1. You can have more than one space before entering a string;

2. Encounters '-' or ' + ' or numeric characters starting with multiple numeric characters consecutively. That is encountered other characters end;

3. Multiple consecutive numeric characters may be followed by other characters, but not integers;

4. When the input is empty, or is a string that cannot be converted, output 0;

5. When the integer is greater than 2147483647, the output is 2147483647. When less than-2147483648, then output-2147483648

Idea: The main is to pay attention to overflow situation, in the process of traversal to determine whether overflow, or the final result can be more than 64 bits.

1 classSolution {2  Public:3     intMyatoi (stringstr) {4         intI=0, len=str.length ();5         if(len==0)6           return 0;7         intflag=0;8          while(i<len&&str[i]==' '){9i++;Ten         } One         if(str[i]=='-') A          { -flag=1; -i++; the          } -          Else if(str[i]=='+') -          { -i++; +          } -          Else if(str[i]<'0'|| Str[i]>'9') +          { A              return 0; at          } -         Long Longsum=0; -          while(i<Len) { -             if(str[i]>='0'&&str[i]<='9') -               { -sum=sum*Ten+ (str[i]-'0'); in                   if(sum>2147483647) -                       Break; to               } +             Else -                 Break; thei++; *         } $         intresult=sum;Panax Notoginseng         if(sum>2147483647){ -             if(flag) the              return-2147483648; +             Else A              return 2147483647; the         } +         Else -         { $             if(flag) $               return-result; -             Else -               returnresult; the         } -     }Wuyi};

Leetcode 8. String to Integer (atoi)