produce intersection and decomposition lists with two generic lists

Suppose that we have two List<int>'s

List<int> list1 = new List<int> { 1, 3, 5, 7 , 9, 11, 18 };
List<int> list2 = new List<int> { 2, 3, 5, 7 , 9, 10, 20, 26, 36 };

question how can i produce;

intersect  {3, 5, 开发者_StackOverflow社区7, 9 }
list1Decomp  { 1, 11, 18 }
list2Decomp  { 2, 10, 20, 26, 36 }

thanks in advance.

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var intersection = list1.Intersect(list2).ToList();
var list1Decomp = list1.Except(intersection).ToList();
var list2Decomp = list2.Except(intersection).ToList();

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var intersect = list1.Intersect(list2);
var list1Decomp = list1.Except(list2);
var list2Decomp = list2.Except(list1);

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In short:

 intersect = list1.Intersect(list2);
 list1Decomp = list1.Except(list2);
 list2Decomp = list2.Except(list1);

These algorithms would be most efficient on an ordered collection (HashSet<> e.g.)

Also beware of using these algorithms on collections of custom types; they really need good IEquatable<> support (i.e. implement the interface and provide your own GetHashCode and Equals). Otherwise, the results will be not what you expect

Although you didn't ask, you might have:

 symmDifference = list1.Union(list2).Except(list1.Intersect(list2))

or

 symmDifference = new HashSet<int>(list1).SymmetricExceptWith(list2)