class Solution {
public:
    int strToInt(string str) {
        int k=0;
        while(k<str.size()&&str[k]==' ') k++;
        long long res=0;

        int minus=1;
        if(k<str.size())
        {
            if(str[k]=='-') minus=-1,k++;
            else if(str[k]=='+') k++;
        }
        while(k<str.size()&&str[k]>='0'&&str[k]<='9')
        {
            res=res*10+str[k]-'0';  //变为实际数字
            if(res>1e11) break;
            k++;

        }
        res*=minus;
        if(res>INT_MAX)  res=INT_MAX;
        if(res<INT_MIN)  res=INT_MIN;

        return res;
    }
};