20180207StrToInt

//有问题
class Solution {
public:
    enum status {k1=0,k2};
    int curstatus=k1;
    int StrToInt(string str) {
        curstatus=k2;
        long long result=0;
        int i=0;
        if(str.length()>0&&str[i]!='\0'){
            bool flag=false;
            if(str[i]=='+')
                i++;
            else if(str[i]=='-'){
                flag=true;
                i++;
            }
            if(str[i]!='\0')
                result=change(str,flag,i);
        }
        return (int)result;
    }
    long long change(string str,bool flag,int i){
        long long num=0;
        while(str[i]!='\0'){
            if(str[i]>='0'&&str[i]<='9'){
                int a=flag?-1:1;
                num=num*10+a*(str[i]-'0');
                if((!flag&&num>0x7FFFFFFF)||(flag&&num<0x80000000)){
                    num=0;
                    break;
                }
                i++;
            }else{
                num=0;
                break;
            }
        }
        if(str[i]=='\0')
            curstatus=k1;
        return num;
    }
};