- test iterator first on all iterable data structures

lists/arraylist/arraylist_test.go

@@ -393,6 +393,21 @@ func TestListIteratorReset(t *testing.T) {
 	}
 }
 
+func TestListIteratorFirst(t *testing.T) {
+	list := New()
+	it := list.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	list.Add("a", "b", "c")
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "a")
+	}
+}
+
 func TestListIteratorLast(t *testing.T) {
 	list := New()
 	it := list.Iterator()

lists/doublylinkedlist/doublylinkedlist_test.go

@@ -393,6 +393,21 @@ func TestListIteratorReset(t *testing.T) {
 	}
 }
 
+func TestListIteratorFirst(t *testing.T) {
+	list := New()
+	it := list.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	list.Add("a", "b", "c")
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "a")
+	}
+}
+
 func TestListIteratorLast(t *testing.T) {
 	list := New()
 	it := list.Iterator()

lists/singlylinkedlist/singlylinkedlist_test.go

@@ -352,6 +352,21 @@ func TestListIteratorReset(t *testing.T) {
 	}
 }
 
+func TestListIteratorFirst(t *testing.T) {
+	list := New()
+	it := list.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	list.Add("a", "b", "c")
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "a")
+	}
+}
+
 func BenchmarkList(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		list := New()

maps/treemap/treemap_test.go

@@ -422,6 +422,20 @@ func TestMapIteratorReset(t *testing.T) {
 	}
 }
 
+func TestMapIteratorFirst(t *testing.T) {
+	m := NewWithIntComparator()
+	m.Put(3, "c")
+	m.Put(1, "a")
+	m.Put(2, "b")
+	it := m.Iterator()
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
+	}
+}
+
 func TestMapIteratorLast(t *testing.T) {
 	m := NewWithIntComparator()
 	m.Put(3, "c")

sets/treeset/treeset_test.go

@@ -292,6 +292,18 @@ func TestSetIteratorReset(t *testing.T) {
 	}
 }
 
+func TestSetIteratorFirst(t *testing.T) {
+	set := NewWithStringComparator()
+	set.Add("a", "b", "c")
+	it := set.Iterator()
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "a")
+	}
+}
+
 func TestSetIteratorLast(t *testing.T) {
 	set := NewWithStringComparator()
 	set.Add("a", "b", "c")

stacks/arraystack/arraystack_test.go

@@ -192,6 +192,23 @@ func TestStackIteratorReset(t *testing.T) {
 	}
 }
 
+func TestStackIteratorFirst(t *testing.T) {
+	stack := New()
+	it := stack.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	stack.Push("a")
+	stack.Push("b")
+	stack.Push("c")
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "c" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "c")
+	}
+}
+
 func TestStackIteratorLast(t *testing.T) {
 	stack := New()
 	it := stack.Iterator()

stacks/linkedliststack/linkedliststack_test.go

@@ -152,6 +152,23 @@ func TestStackIteratorReset(t *testing.T) {
 	}
 }
 
+func TestStackIteratorFirst(t *testing.T) {
+	stack := New()
+	it := stack.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	stack.Push("a")
+	stack.Push("b")
+	stack.Push("c")
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != "c" {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, "c")
+	}
+}
+
 func BenchmarkStack(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		stack := New()

trees/binaryheap/binaryheap_test.go

@@ -192,12 +192,12 @@ func TestBinaryHeapIteratorPrev(t *testing.T) {
 }
 
 func TestBinaryHeapIteratorReset(t *testing.T) {
-	tree := NewWithIntComparator()
-	it := tree.Iterator()
+	heap := NewWithIntComparator()
+	it := heap.Iterator()
 	it.Reset()
-	tree.Push(2)
-	tree.Push(3)
-	tree.Push(1)
+	heap.Push(2)
+	heap.Push(3)
+	heap.Push(1)
 	for it.Next() {
 	}
 	it.Reset()
@@ -207,6 +207,23 @@ func TestBinaryHeapIteratorReset(t *testing.T) {
 	}
 }
 
+func TestStackIteratorFirst(t *testing.T) {
+	heap := NewWithIntComparator()
+	it := heap.Iterator()
+	if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	heap.Push(3) // [3]
+	heap.Push(2) // [2,3]
+	heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if index, value := it.Index(), it.Value(); index != 0 || value != 1 {
+		t.Errorf("Got %v,%v expected %v,%v", index, value, 0, 1)
+	}
+}
+
 func TestBinaryHeapIteratorLast(t *testing.T) {
 	tree := NewWithIntComparator()
 	it := tree.Iterator()

trees/redblacktree/redblacktree_test.go

@@ -512,6 +512,20 @@ func TestRedBlackTreeIteratorReset(t *testing.T) {
 	}
 }
 
+func TestRedBlackTreeIteratorFirst(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
+	}
+}
+
 func TestRedBlackTreeIteratorLast(t *testing.T) {
 	tree := NewWithIntComparator()
 	tree.Put(3, "c")