输入1 67 256 43 这样的一串数字,如何用上所有的数字构成一个最大的数字

private int[] num = new int[4] { 3111, 311, 31, 2 };

        private void ReturnNum()

        {

            int k;

            for (int i = num.Length - 1; i > 0; i--)

            {

                for (int j = i; j >0; j--)

                {

                    if (GetBig(num[j], num[j - 1]))

                    {

                        k = num[j];

                        num[j] = num[j - 1];

                        num[j - 1] = k;

                    }

                }

            }

            int xx = 0;

        }

        private bool GetBig(int n1, int n2)

        {

            int n1begin = int.Parse(n1.ToString().Substring(0,1));

            int x1 = n1;

            int x2 = n2;

            

            if (n1 == n2)

            {

                x1 = n1 * 10 + n1begin;

                x2 = n2 * 10 + n1begin;

            }

            return bijiao(x1.ToString(),x2.ToString());

        }

        private bool bijiao(string x1,string x2)

        {

            int y1 = int.Parse(x1 + x2);

            int y2 = int.Parse(x2 + x1);

            return y1 > y2;

        }

string i2str(int i)

{

   stringstream stream;

   stream << i;

   return stream.str();

}



bool comp(int i1, int i2)

{

    string str1 = i2str(i1);

    string str2 = i2str(i2);

    return (str1+str2 > str2+str1);

}



int main()

{

    vector<int> vecElem;

    //init vecElem



    sort(vecElem.begin(), vecElem.end(), comp);



    string str;

    for (int i = 0; i < (int)vecElem.size(); i++) {

	str += i2str(vecElem[i]); 

    }



    cout << str << endl;

}