Reverse Integer

 1 class Solution {
 2 public:
 3     int reverse(int x) {
 4         if(x == -2147483648) return 0;
 5         string s;
 6         int positive = 1;
 7         if(x < 0) {x = -x; positive = -1;}
 8         while(x){
 9             char temp = x % 10 + ‘0‘;
10             s += temp;
11             x /= 10;
12         }
13         int result = string2int(s);
14         if(result){
15             if(positive == -1) return -result;
16             return result;
17         }
18         return 0;
19     }
20     
21     int string2int(string s){
22         if(s.length() > 10 || (s.length() == 10 && s[0] > ‘2‘)) return 0;
23         double result = 0;
24         int exponential = 1;
25         for(int i = s.length() - 1; i >= 0; i--){
26             int temp = s[i] - ‘0‘;
27             result += temp * exponential;
28             exponential *= 10;
29         }
30         if(result > 2147483647.0) return 0;
31         return result;
32     }
33 };