个人觉得01背包解最简单，只是时间复杂度需优化。

public static void MultipleEle(int []source, int sum)

{

    List<int> tmp = new List<int>();

    MultipleEleCore(source, sum, source.Length - 1, tmp);

}

public static void MultipleEleCore(int []source, int sum, int index, List<int>ilist)

{

if (source == null || ilist == null || source.Length == 0)

    {

return;

    }

    if (index < 0)

    {

    return;

    }

    if (sum == source[index])

    {

//if (ilist.Count == 2)

{

Console.Write(source[index] + " ");

foreach (int item in ilist)

{

Console.Write(item + " ");

}

Console.WriteLine();

}

    }

    ilist.Insert(0, source[index]);

    MultipleEleCore(source, sum - source[index], index - 1, ilist);

    ilist.RemoveAt(0);

    MultipleEleCore(source, sum, index - 1, ilist);

}