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class Solution {
public:
int StrToInt(string str) {
int len = str.size();
if(len == 0||str.empty()) return 0;
int sum =0;
char zero = 0+'0';
char nine = 9+'0';
bool flag =true;
bool flg =false;
if(str[0]=='-') flag = false;
if(str[0]=='+') flg =true;
if(flag){
if(!flg){
for(int i=0;i<len;i++){
if(str[i]>=zero && str[i]<=nine){
sum = sum*10 + (str[i] - '0');
}
else return 0;
}
return sum;}
else{
for(int i=1;i<len;i++){
if(str[i]>=zero && str[i]<=nine){
sum = sum*10 + (str[i] - '0');
}
else return 0;
}
return sum;
}
}
if(!flag){
for(int i=1;i<len;i++){
if(str[i]>=zero && str[i]<=nine){
sum = sum*10 + (str[i] - '0');
}
else return 0;
}
return -sum;
}
return 0;
}
};