[演算法笔记]英文單字從單數變複數

void plural(string s)
{
    int n = s.length();
    if (s.back() == 'y')
        cout << s.substr(0, n-1) << "ies";
    else if (s.back() == 's' || s.back() == 'x')
        cout << s << "es";
    else if (s.substr(n-2) == "sh" || s.substr(n-2) == "ch")
        cout << s << "es";
    else if (s.substr(n-3) == "man")
        cout << s.substr(0, n-3) << "men";
    else
        cout << s << 's';
}