【leetcode】Valid Number

 1 class Solution {
 2 public:
 3  
 4     enum TYPE
 5     {
 6         INVALID,
 7         SPACE,
 8         SIGN,
 9         DIGIT,
10         DOT,
11         EXP
12     };
13    
14     bool isNumber(const char *s) {
15        
16         while(*s!=‘\0‘&&*s==‘ ‘) s++;
17         if(*s==‘+‘||*s==‘-‘) s++;
18  
19        
20         if(strlen(s)==0) return false;
21        
22         bool hasSign=false;
23         bool hasDigit=false;
24         bool hasDot=false;
25         bool hasExp=false;
26        
27         TYPE preType;
28         TYPE type;
29         while(*s!=‘\0‘)
30         {
31             type=getType(s);
32            
33             if(type==INVALID) return false;
34            
35             if(preType==SIGN &&(type!=DIGIT&&type!=DOT)) return false;
36             if(preType==DOT&&(type!=DIGIT&&type!=SPACE&&type!=EXP))return false;
37             if(preType==EXP&&(type!=DIGIT&&type!=SIGN))return false;
38             if(preType==SPACE&&type!=SPACE)return false;
39            
40            
41             switch(type)
42             {
43                 case SPACE:
44                     preType=SPACE;
45                     break;
46                 case SIGN:
47                     if(hasSign) return false;
48                     else
49                     {
50                         if(preType!=EXP) return false;
51                         hasSign=true;
52                         preType=SIGN;
53                     }
54                     break;
55                 case DIGIT:
56                     hasDigit=true;
57                     preType=DIGIT;
58                     break;
59                 case DOT:
60                     if(hasDot||hasExp) return false;
61                     else
62                     {
63                         hasDot=true;
64                         preType=DOT;
65                     }
66                     break;
67                 case EXP:
68                     if(hasExp||!hasDigit) return false;
69                     else
70                     {
71                         hasExp=true;
72                         preType=EXP;
73                     }
74                     break;
75             }
76             s++;
77         }
78        
79         if(preType==SIGN||preType==EXP||(!hasDigit&&hasDot)) return false;
80        
81         return true;
82     }
83    
84    
85     TYPE getType(const char *s)
86     {
87         if(*s==‘ ‘) return SPACE;
88         else if(*s==‘+‘||*s==‘-‘) return SIGN;
89         else if(isdigit(*s))return DIGIT;
90         else if(*s==‘.‘)return DOT;
91         else if(*s==‘e‘)return EXP;
92         else return INVALID;
93     }
94 };