[LeetCode] Valid Number

 1 class Solution {
 2 public:
 3     bool isNumber(string s) {
 4         int i = 0, n = s.length();
 5         // Skip the leading spaces
 6         while (i < n && isspace(s[i])) i++;
 7         // Skip the sign
 8         if (s[i] == '+' || s[i] == '-') i++;
 9         // Check for the following significant parts
10         int digits = 0, dots = 0;
11         while (i < n && (isdigit(s[i]) || s[i] == '.')) {
12             if (isdigit(s[i])) digits++;
13             else dots++;
14             i++;
15         }
16         if (digits < 1 || dots > 1) return false;
17         if (i == n) return true;
18         // Check for the exponential parts
19         if (s[i] == 'e') {
20             i++;
21             if (i == n) return false;
22             if (s[i] == '+' || s[i] == '-') i++;
23             digits = 0;
24             while (i < n && (isdigit(s[i]))) {
25                 digits++;
26                 i++;
27             }
28             if (digits < 1) return false;
29         }
30         // Skip the trailing spaces
31         while (i < n && isspace(s[i])) i++;
32         return i == n;
33     }
34 };