C# 合并只要有交集的所有集合

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace ConsoleApplication2
 {
     class Program
     {
         static void Main(string[] args)
         {

             List<int> list1 = new List<int> { , ,  };
             List<int> list2 = new List<int> { , ,  };
             List<int> list3 = new List<int> { , ,  };

             List<int> list4 = new List<int> { , ,  };
             List<int> list5 = new List<int> { , ,  };

             List<int> list6 = new List<int> { , ,  };
             List<int> list7 = new List<int> { , ,  };

             List<List<int>> list = new List<List<int>>();
             list.Add(list1);
             list.Add(list2);
             list.Add(list3);
             list.Add(list4);
             list.Add(list5);
             list.Add(list6);
             list.Add(list7);

             List<int> allint = new List<int>();//所有的集合数据
             HashSet<int> repeated = new HashSet<int>(); //得到没有重复的hashset
             foreach (List<int> item in list)
             {
                 foreach (int index in item)
                 {
                     if (allint.Contains(index))
                         repeated.Add(index);//得到所有重复的集合的元素
                     allint.Add(index);//得到所有的集合的元素
                 }
             }

             foreach (var setkey in repeated)//循环重复的值
             {
                 List<int> templist = null;//临时
                 List<List<int>> removelist = new List<List<int>>();
                 foreach (var item in list)//循环
                 {
                     //if (templist == null)
                     //{
                     //    templist = item;
                     //    removelist.Add(item);
                     //}

                     //if (item.Contains(setkey))
                     //{
                     //    removelist.Add(item);
                     //    templist = templist.Union(item).ToList();
                     //}

                     if (item.Contains(setkey))
                     {
                         if (templist == null)
                         {
                             templist = item;
                             removelist.Add(item);
                         }
                         else
                         {
                             removelist.Add(item);
                             templist = templist.Union(item).ToList();
                         }
                     }
                 }
                 foreach (var item in removelist)
                 {
                     list.Remove(item);
                 }
                 removelist.Clear();
                 list.Add(templist);
             }

             foreach (var item in list)
             {
                 foreach (var item1 in item)
                 {
                     Console.Write(item1 + " , ");
                 }
                 Console.Write("\r\n");
             }
             Console.ReadKey();
         }

     }
 }