/// 
        ///  Find all sub number groups that sum equal to a given number        /// 
        /// sorted list        /// total number        /// 
     
      all sub number groups
             private static IEnumerable
     
      
       > FindCombination(List
       
         list, int total)        {            var found = new List
        
         
          >();            //[2,3,4]  total:1            if (list.First() > total)                return found;            //[2]   total:1            if (list.Count == 1 && list.First() != total)                return found;            //[1,2, 6] => [1,2]            if (list.Contains(total))            {                found.Add(new List
          
            { total }); list.Remove(total); } //[1,2,3] => 1+2+3 =6 if (list.Sum() == total) { found.Add(list); return found; } //travel every item to find combination for (var i = 0; i < list.Count; i++) { var seed = list[i]; var subTotal = total - seed; var clonedList = new List
           
            (list); clonedList.RemoveAt(i); var combinations = FindCombination(clonedList, subTotal); foreach (var item in combinations) { item.Add(seed); item.Sort(); if (!IsContainArray(found, item)) found.Add(item); } } return found; } /// 
            
 /// To check if an list of list contains a list /// 
 /// 
             /// 
             /// 
            
             contains or not
             private static bool IsContainArray(IEnumerable
            
             
              > list, IEnumerable
              
                item) { return list.Select(l => string.Join(",", l)).Contains(string.Join(",", item)); }
              
             
            
           
          
         
        
       
      
     

这个算法可以说是纯为实现而实现，没有经过任何精巧设计，但从测试结果来看，还没找到漏掉的。