bag, queue

fundamentals/bag/bag.go

@@ -0,0 +1,51 @@
+package bag
+
+// "Generic" item.
+// When type parameters will land this type became
+// type Item[T any] T
+type Item interface{}
+
+type Bag interface {
+	Add(Item)
+	Size() int
+	IsEmpty() bool
+	ForEach(func(Item))
+}
+
+// We use linked list as internal data structure
+// to get O(1) speed for Add operation
+type node struct {
+	item Item
+	next *node
+}
+
+type bag struct {
+	size int
+	head *node
+}
+
+func NewBag() Bag {
+	return &bag{}
+}
+
+func (b *bag) Add(item Item) {
+	next := b.head
+	b.head = &node{item, next}
+	b.size++
+}
+
+func (b *bag) Size() int {
+	return b.size
+}
+
+func (b *bag) IsEmpty() bool {
+	return b.size == 0
+}
+
+// As for now Go doesn't have iterators.
+// But we can simulate them with ForEach method
+func (b *bag) ForEach(f func(Item)) {
+	for current := b.head; current != nil; current = current.next {
+		f(current.item)
+	}
+}

fundamentals/bag/bag_test.go

@@ -0,0 +1,36 @@
+package bag
+
+import (
+	"log"
+	"testing"
+)
+
+func TestSimple(t *testing.T) {
+	bag := NewBag()
+	sum := 0
+
+	bag.Add(1)
+	bag.Add(2)
+	bag.Add(3)
+
+	bag.ForEach(func(i Item) { sum += i.(int) })
+
+	if sum != 6 {
+		log.Fatal("wrong items in bag")
+	}
+}
+
+func TestEmpty(t *testing.T) {
+	bag := NewBag()
+	sum := 0
+
+	if bag.Size() != 0 || !bag.IsEmpty() {
+		log.Fatal("bag should be empty")
+	}
+
+	bag.ForEach(func(i Item) { sum += i.(int) })
+
+	if sum != 0 {
+		log.Fatal("wrong items in bag")
+	}
+}

fundamentals/queue/queue.go

@@ -0,0 +1,59 @@
+package queue
+
+// "Generic" item.
+// When type parameters will land this type became
+// type Item[T any] T
+type Item interface{}
+
+type Queue interface {
+	Enqueue(Item)
+	Dequeue() Item
+	Size() int
+	IsEmpty() bool
+}
+
+// We use linked list as internal data structure
+// to get O(1) speed for push and pop opeartions
+type node struct {
+	item Item
+	next *node
+}
+
+type queue struct {
+	size int
+	head *node
+	tail *node
+}
+
+func NewQueue() Queue {
+	return &queue{}
+}
+
+func (q *queue) Enqueue(item Item) {
+	oldTail := q.tail
+	q.tail = &node{item: item, next: nil}
+	if q.IsEmpty() {
+		q.head = q.tail
+	} else {
+		oldTail.next = q.tail
+	}
+	q.size++
+}
+
+func (q *queue) Dequeue() Item {
+	first := q.head
+	q.head = q.head.next
+	if q.IsEmpty() {
+		q.tail = nil
+	}
+	q.size--
+	return first.item
+}
+
+func (q *queue) Size() int {
+	return q.size
+}
+
+func (q *queue) IsEmpty() bool {
+	return q.head == nil
+}

fundamentals/queue/queue_test.go

@@ -0,0 +1,35 @@
+package queue
+
+import (
+	"log"
+	"testing"
+)
+
+func TestSimple(t *testing.T) {
+	queue := NewQueue()
+
+	queue.Enqueue(10)
+	queue.Enqueue(20)
+	queue.Enqueue(30)
+
+	first, second := queue.Dequeue().(int), queue.Dequeue().(int)
+
+	if first != 10 && second != 20 {
+		log.Fatal("wrong order")
+	}
+}
+
+func TestSize(t *testing.T) {
+	queue := NewQueue()
+
+	if queue.Size() != 0 {
+		log.Fatal("empty queue should have size 0")
+	}
+	queue.Enqueue(10)
+	queue.Enqueue(20)
+	queue.Enqueue(30)
+
+	if queue.Size() != 3 {
+		log.Fatal("wrong size")
+	}
+}