LeetCodeOnlineJudge题目C#练习-ValidNumber

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Validate if a given string is numeric
Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true
Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

 1         public static bool ValidNumber(string s)
 2         {
 3             s = s.Trim();
 4             int eindex = s.IndexOf('e');
 5 
 6             if (eindex == -1)
 7                 return isValidNumber(s);
 8 
 9             string s1 = s.Substring(0, eindex);
10             string s2 = s.Substring(eindex + 1);
11             return isValidNumber(s1) && isValidNumber(s2);
12         }
13 
14         public static bool isValidNumber(string s)
15         {
16             int dot = 0;
17             for (int i = 0; i < s.Length; i++)
18             {
19                 // not valid char?
20                 if (s[i] != '+' && s[i] != '-' && s[i] != '.' && !(s[i] >= '0' && s[i] <= '9'))
21                     return false;
22 
23                 // '+' or '-' in the middle?
24                 if (i > 0 && (s[i] == '+' || s[i] == '-'))
25                     return false;
26 
27                 // more than two '.'?
28                 if (s[i] == '.' && dot > 0)
29                     return false;
30                 // count dot
31                 else if(s[i] == '.')
32                     dot++;
33             }
34 
35             return true;
36         }