【leetcode刷题笔记】Valid Number

 1 public class Solution {
 2     public boolean isNumber(String s) {
 3         if(s == null || s.length() == 0)
 4             return false;
 5         
 6         s = s.trim();
 7         if(s.length() == 0)
 8             return false;
 9         
10         int i = 0;
11         if(s.charAt(0) == ‘+‘ || s.charAt(0) == ‘-‘)
12             i++;
13        
14         boolean hasDot = false;
15         boolean hasExp = false;
16         boolean num = false;
17         
18         while(i<s.length()){
19             char now = s.charAt(i);
20             if(now >= ‘0‘ && now <= ‘9‘)
21             {
22                 num = true;
23             }
24             else if(now == ‘.‘){
25                 if(hasDot || hasExp)
26                     return false;
27                 hasDot = true;
28             }
29             else if(now == ‘e‘){
30                 if(hasExp || num == false)
31                     return false;
32                 hasExp = true;
33                 num = false;
34             }
35             else if(now == ‘+‘ || now == ‘-‘){
36                 if(s.charAt(i-1) != ‘e‘)
37                     return false;
38             }
39             else
40                 return false;
41             i++;                
42         }
43         return num;
44     }
45 }