8. String to Integer (atoi)

static int wing=[]()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();

class Solution 
{
public:
    int myAtoi(string str) 
    {
        int flag=1,i=0,base=0;
        while(str[i]==' ')
            i++;
        if(str[i]=='-'||str[i]=='+')
        {
            flag= (str[i]=='-')?-1:1;
            i++;
        }
        while(isdigit(str[i]))
        {
            if(base>INT_MAX/10||(base==INT_MAX/10&&str[i]-'0'>7))
                return flag==1? INT_MAX:INT_MIN;
            base=10*base+(str[i++]-'0');
        }
        return base*flag;
    }
};

边扫描边转换，同时判定溢出。