class Solution {public:    const int _MAX=0x7fffffff,_MIN=0x80000000;    int myAtoi(string str) {        long long int val=0;        int i=0,flag=1;        while(str[i]==' ') ++i;        if(str[i]=='-') flag=-1,++i;        else if(str[i]=='+') ++i;        while(i
    
     ='0' && str[i]<='9'){            val=val*10+str[i]-'0';            if(flag*val>=_MAX) return _MAX;            if(flag*val<=_MIN) return _MIN;            ++i;        }        return flag*val;    }};