Find "not the same" elements in two arrays

Question

I have two whole lists ( List<int> ). They contain the same elements, but list 1 contains elements that are not in list 2.

How to find which elements of list 1 DO NOT appear in list 2.

Thanks:)

PS. lang - c #

Answer 1

 new HashSet<int>(l1).ExceptWith(l2); 

Answer 2

You can use IEnumerable.Except :

 list1.Except(list2); 

Answer 3

A very simple solution:

 HashSet<int> theSet1 = new HashSet<int>(List1); theSet1.ExceptWith(List2); 

Answer 4

For simplicity, you can use the Contains method and check one list that does not contain an element of another:

 for (int i = 0; i < list2.Count; ++i) { if (!list1.Contains(list2[i]) //current element is not in list 1 //some code } 

Answer 5

If your solution is that the first list contains the second and you want the onli entries added after the first list, Maybe this will be useful

 public static int DokleSuIsti(IList<string> prevzemNow, IList<string> prevzemOld) { int dobroja = 0; int kolikohinaje; if (prevzemOld.Count() < prevzemNow.Count()) { kolikohinaje = prevzemOld.Count(); } else { kolikohinaje = prevzemNow.Count(); } for (int i = 0; i < kolikohinaje; i++) { if (!Object.Equals(prevzemNow[i], prevzemOld[i])) { dobroja = i; return dobroja; } dobroja = i; } return dobroja; } 

After that, you can use this int as a starting point for going through your Ilist

Answer 6

If they are not sorted or something else, it will be difficult for you.

Any O (N ^ 2) algorithm (simple, stupid loop) or additional data structures tell me what you prefer.

Or you can, of course, change the source data by sorting, which I suppose is not an option.