把字符串转换成整数

 1 class Solution {
 2 public:
 3     int StrToInt(string str) {
 4         if(str.length() == 0)
 5             return 0;
 6         bool fu = str[0] == ‘-‘;
 7         if(fu)
 8             str.erase(str.begin());
 9         if(str[0] == ‘+‘)
10             str.erase(str.begin());
11         int num = 0,len = str.length();
12         for (int i = 0;i < len ; ++i)
13         {
14             if(str[i] >= ‘0‘ && str[i] <= ‘9‘)
15              num = num*10 + str[i] - ‘0‘;
16             else return 0;
17         }
18         if(fu)
19             num = -1 * num;
20         return num;
21     }
22 };