bool isUnsigned(const string& s)
{
    if(s.empty()) return false;
        return all_of(s.begin(), s.end(), [](unsigned char ch) {return isdigit(ch); });
}

bool isInt(const string& s)
{
    if (s.empty()) return false;
    string::size_type start = (s.front() == '+' || s.front() == '-' ? 1 : 0);
    return isUnsigned(s.substr(start));
}

bool isRational(const string& s)
{
    if (s.empty()) return false;
    auto end = s.rfind('.');
    if (end == string::npos) return isInt(s);
    else
    {
        string::size_type start = (s.front() == '+' || s.front() == '-' ? 1 : 0);
            auto isEmpty = start == end;
        if (!isEmpty && !isInt(s.substr(0, end))) return false;
        if (isEmpty && end == s.size() - 1) return false;
        if (end != s.size() -1 && !isUnsigned(s.substr(end + 1))) return false;
    }
    return true;
}

class Solution {
public:
    bool isNumber(string& s)
        {
        s.erase(s.begin(), find_if(s.begin(), s.end(), [](unsigned char ch) {return !isspace(ch); }));
        s.erase(find_if(s.rbegin(), s.rend(), [](unsigned char ch) {return !isspace(ch); }).base(), s.end());
        auto ePos = s.find('e');
        if (ePos == string::npos) return isRational(s);
        return isRational(s.substr(0, ePos)) && isInt(s.substr(ePos + 1));
    }
};