Added more tests

Author: RealA10N

dsu.go

@@ -12,8 +12,8 @@ type Dsu struct {
 // The element values are not stored explicitly in the data structure,
 // and the user of the data structure is responsible for maintaining
 // a correspondence between the element values and their indices.
-func NewDsu(n uint) *Dsu {
-	dsu := &Dsu{
+func NewDsu(n uint) Dsu {
+	dsu := Dsu{
 		parent: make([]uint, n),
 		size:   make([]uint, n),
 	}

dsu_test.go

@@ -16,3 +16,21 @@ func TestSimpleUnion(t *testing.T) {
 		t.Error("2 should not be in the same set as 0 and 1")
 	}
 }
+
+func TestDoubleUnion(t *testing.T) {
+	d := dsu.NewDsu(3)
+	d.Union(0, 1)
+	d.Union(1, 2)
+	if d.Find(0) != d.Find(1) || d.Find(1) != d.Find(2) || d.Find(0) != d.Find(2) {
+		t.Error("0, 1, and 2 should be in the same set")
+	}
+}
+
+func TestUnionOfSameSet(t *testing.T) {
+	d := dsu.NewDsu(2)
+	d.Union(0, 1)
+	d.Union(0, 1)
+	if d.Find(0) != d.Find(1) {
+		t.Error("0 and 1 should be in the same set")
+	}
+}