Valid Number

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.

思路：

需要注意的地方：

1、其实的空格

2、e的次数，以及e前后都要有数字

3、小数点的次数，以及小数点不能前后都没有数字

4、开始和e之后可以有'+''-'

代码：

 1     bool isNumber(const char *s) {
 2         while(*s == ' ')
 3             s++;
 4         if(*s == '+' || *s == '-')
 5             s++;
 6         int l = strlen(s);
 7         if(l == 0)
 8             return false;
 9         int eNum = 0, pointNum = 0;
10         bool beforeE = false, beforePoint = false, afterE = false, afterPoint = false;
11         int i;
12         for(i = 0; i < l; i++){
13             if(s[i] >= '0' && s[i] <= '9'){
14                 if(eNum == 0)
15                     beforeE = true;
16                 else
17                     afterE = true;
18                 if(pointNum == 0)
19                     beforePoint = true;
20                 else
21                     afterPoint = true;
22                 continue;
23             }
24             else if(s[i] == 'e'){
25                 if(eNum == 0){
26                     eNum++;
27                     if(s[i+1] == '+' || s[i+1] == '-')
28                         i++;
29                 }
30                 else
31                     return false;
32             }
33             else if(s[i] == '.'){
34                 if(pointNum > 0 || eNum > 0)
35                     return false;
36                 pointNum++;
37             }
38             else if(s[i] == ' '){
39                 while(s[i] == ' ')
40                     i++;
41                 if(s[i] != '\0')
42                     return false;
43                 else
44                     break;
45             }
46             else
47                 return false;
48         }
49         if(eNum == 1 && !(beforeE && afterE))
50             return false;
51         if(pointNum == 1 && !afterPoint && !beforePoint)
52             return false;
53         return true;
54     }

 

posted on 2013-12-04 17:14  waruzhi  阅读(216)  评论(0)  编辑  收藏  举报

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