代码改变世界

leetcode - Valid Number

2013-11-20 15:54  张汉生  阅读(198)  评论(0)    收藏  举报

 

 1 class Solution {
 2 public:
 3     bool isInt(const char * s, int start, int end){
 4         if (end < start)
 5             return false;
 6         if  (start<=end && (s[start] == '+' || s[start] == '-'))
 7             start++;
 8         if (end<start)
 9             return false;
10         for (int i = start; i <= end; i++){
11             if (s[i]<'0' || s[i]>'9')
12                 return false;
13         }
14         return true;
15     }
16     bool isDouble(const char * s, int start, int end){
17         if (start <= end && (s[start] == '+' || s[start] == '-'))
18             start++;
19         for (int i = start; i <= end; i++){
20             if (s[i] == '.'){
21                 if (i + 1 <= end && (s[i + 1] == '-' || s[i + 1] == '+'))
22                     return false;
23                 if (i == start)
24                     return isInt(s, i + 1, end);
25                 else if (i == end)
26                     return isInt(s, start, i-1);
27                 else return isInt(s, start, i - 1) && isInt(s, i + 1, end);
28             }
29         }
30         return isInt(s, start, end);
31     }
32     bool isNumber(const char *s) {
33         // Note: The Solution object is instantiated only once and is reused by each test case.
34         int len = strlen(s);
35         int start = 0, end = len - 1;
36         while (start <= end && (s[start] == ' '))
37             start++;
38         while (end >= start && s[end] == ' ')
39             end--;
40         for (int i = start; i <= end; i++){
41             if (s[i] == 'e' || s[i] == 'E'){
42                 return isDouble(s, start, i - 1) && isInt(s, i + 1, end);
43             }
44         }
45         return isDouble(s, start , end);
46     }
47 };