add intersection for unsorted lists

Changed the way the intersection is computed. An intersection does
not return duplicate values. So the result is like a set.

primitiveCollections/src/test/java/org/lucares/collections/IntListTest.java

@@ -1094,21 +1094,56 @@ public class IntListTest {
 			Assert.assertEquals(IntList.of(2, 4), actual);
 		}
 
+		{
+			final IntList a = IntList.of(0, 2, 4, 6);
+			final IntList b = IntList.of(3, 5);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(), actual);
+		}
+
 		/*
-		 * cardinality of elements that occur multiple time is equal to the minimum
-		 * cardinality in either list
+		 * duplicate elements are removed in the result
 		 */
 		{
 			final IntList a = IntList.of(3, 3, 3);
 			final IntList b = IntList.of(3, 3);
 			final IntList actual = IntList.intersection(a, b);
-			Assert.assertEquals(IntList.of(3, 3), actual);
+			Assert.assertEquals(IntList.of(3), actual);
 		}
 		{
-			final IntList a = IntList.of(4);
+			final IntList a = IntList.of(4, 4);
 			final IntList b = IntList.of(4, 4, 4);
 			final IntList actual = IntList.intersection(a, b);
 			Assert.assertEquals(IntList.of(4), actual);
 		}
 	}
+
+	@Test
+	public void testIntersectionUnsortedLists() {
+		{
+			final IntList a = IntList.of(0, 1, 2, 3, 4);
+			final IntList b = IntList.of(2, 4, 5);
+			a.shuffle();
+			b.shuffle();
+			final IntList actual = IntList.intersection(a, b);
+			actual.sort();
+			Assert.assertEquals(IntList.of(2, 4), actual);
+		}
+
+		/*
+		 * duplicate elements are removed in the result
+		 */
+		{
+			final IntList a = IntList.of(3, 5, 3, 3, 1);
+			final IntList b = IntList.of(2, 3, 3);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(3), actual);
+		}
+		{
+			final IntList a = IntList.of(1, 4);
+			final IntList b = IntList.of(4, 3, 4, 4, 2);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(4), actual);
+		}
+	}
 }