LeeCode-String to Integer (atoi)

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

 1 class Solution {
 2 public:
 3     int myAtoi(string str) {
 4     long long cur=0;
 5     int num=0,i=0;
 6     int flag1=0,flag2=0;
 7     while(str[i]!=‘\0‘ && str[i]==‘ ‘) i++;
 8     if(str[i]==‘-‘) flag1++,i++;
 9     else if(str[i]==‘+‘) flag2++,i++;
10     for(; str[i]!=‘\0‘; i++)
11     {
12         if(str[i]>=‘0‘ && str[i]<=‘9‘)
13         {
14             if(flag1==2)
15             {
16                 cur=cur*10-(str[i]-‘0‘);
17                 if(cur<-2147483648) return -2147483648;
18             }
19             else if(flag1==1) cur=-str[i]+‘0‘,flag1++;
20             else
21             {
22                 cur=cur*10+(str[i]-‘0‘);
23                 if(cur>2147483647) return 2147483647;
24             }
25         }
26         else break;
27     }
28     num=(int)cur;
29     return num;
30     }
31 };