String to Integer

 1 class Solution {
 2 public:
 3     int atoi(string str) {
 4         int size = str.size();
 5         int x=0,flag=1,i=0;
 6         while(str[i]==‘ ‘)
 7         {
 8             i++;
 9         }
10         if(str[i]==‘-‘)
11             {
12                 flag = -1;
13                 i++;
14             }
15         else if(str[i]==‘+‘)
16             i++;
17         int j = i;
18         while(j<size)
19         {
20             if(str[j]<48 || str[j]>57)
21                {
22                    size = j;
23                    break;
24                } 
25             j++;
26         }
27         while(i<size)
28         {
29             x = x*10 + str[i]-48;
30             i++;
31             if(flag==1&&((x==214748364&&str[i]-48>=7&&str[i]-48<=9) || (x>214748364&&i<size)))
32                 return 2147483647;
33             if(flag==-1&&((x==214748364&&str[i]-48>=8&&str[i]-48<=9) || (x>214748364&&i<size)))
34                 return -2147483648;
35 
36         }
37 
38 
39         return  flag*x;
40     }
41 };