HW4 is completed

Signed-off-by: Pavel Pogodaev <[email protected]>

hw04_lru_cache/cache.go

@@ -9,13 +9,54 @@ type Cache interface {
 }
 
 type lruCache struct {
-	Cache // Remove me after realization.
-
 	capacity int
 	queue    List
 	items    map[Key]*ListItem
 }
 
+type cacheItem struct {
+	key   Key
+	value interface{}
+}
+
+func (l *lruCache) Set(key Key, value interface{}) bool {
+	listItem, success := l.items[key]
+	if success {
+		listItem.Value = cacheItem{
+			key:   key,
+			value: value,
+		}
+		l.queue.MoveToFront(listItem)
+		return true
+	}
+
+	l.items[key] = l.queue.PushFront(cacheItem{
+		key:   key,
+		value: value,
+	})
+
+	if l.queue.Len() > l.capacity {
+		deleteItem := l.queue.Back()
+		l.queue.Remove(deleteItem)
+		delete(l.items, deleteItem.Value.(cacheItem).key)
+	}
+	return success
+}
+
+func (l *lruCache) Get(key Key) (interface{}, bool) {
+	listItem, ok := l.items[key]
+	if ok {
+		l.queue.MoveToFront(listItem)
+		return listItem.Value.(cacheItem).value, ok
+	}
+	return listItem, ok
+}
+
+func (l *lruCache) Clear() {
+	l.queue = NewList()
+	l.items = make(map[Key]*ListItem, l.capacity)
+}
+
 func NewCache(capacity int) Cache {
 	return &lruCache{
 		capacity: capacity,

hw04_lru_cache/cache_test.go

@@ -50,7 +50,35 @@ func TestCache(t *testing.T) {
 	})
 
 	t.Run("purge logic", func(t *testing.T) {
-		// Write me
+		c := NewCache(3)
+
+		wasInCache := c.Set("Antony", 1)
+		require.False(t, wasInCache)
+
+		wasInCache = c.Set("Bob", 2)
+		require.False(t, wasInCache)
+
+		wasInCache = c.Set("Ci", 3)
+		require.False(t, wasInCache)
+
+		val, ok := c.Get("Ci")
+		require.True(t, ok)
+		require.Equal(t, 3, val)
+
+		val, ok = c.Get("Bob")
+		require.True(t, ok)
+		require.Equal(t, 2, val)
+
+		val, ok = c.Get("Antony")
+		require.True(t, ok)
+		require.Equal(t, 1, val)
+
+		wasInCache = c.Set("Daddy", 4)
+		require.False(t, wasInCache)
+
+		val, ok = c.Get("ccc")
+		require.False(t, ok)
+		require.Nil(t, val)
 	})
 }
 

hw04_lru_cache/go.mod

@@ -1,4 +1,4 @@
-module github.com/fixme_my_friend/hw04_lru_cache
+module github.com/pogpp/home_works/hw04_lru_cache
 
 go 1.22
 

hw04_lru_cache/list.go

@@ -17,8 +17,85 @@ type ListItem struct {
 }
 
 type list struct {
-	List // Remove me after realization.
-	// Place your code here.
+	head *ListItem // Указатель на первый элемент
+	tail *ListItem // Указатель на последний элемент
+	size int
+}
+
+func (l *list) Len() int {
+	return l.size
+}
+
+func (l *list) Front() *ListItem {
+	return l.head
+}
+
+func (l *list) Back() *ListItem {
+	return l.tail
+}
+
+func (l *list) PushFront(v interface{}) *ListItem {
+	oldFrontItem := l.Front()
+	item := &ListItem{v, oldFrontItem, nil}
+
+	if oldFrontItem != nil {
+		oldFrontItem.Prev = item
+	}
+
+	l.head = item
+	if l.Back() == nil {
+		l.tail = item
+	}
+	l.size++
+	return item
+}
+
+func (l *list) PushBack(v interface{}) *ListItem {
+	oldTailItem := l.Back()
+	item := &ListItem{
+		Value: v,
+		Next:  nil,
+		Prev:  oldTailItem,
+	}
+	if oldTailItem != nil {
+		oldTailItem.Next = item
+	}
+
+	l.tail = item
+	if l.Front() == nil {
+		l.head = item
+	}
+
+	l.size++
+	return item
+}
+
+func (l *list) Remove(i *ListItem) {
+	nextItem := i.Next
+	prevItem := i.Prev
+
+	if prevItem != nil {
+		prevItem.Next = nextItem
+	}
+
+	if nextItem != nil {
+		nextItem.Prev = prevItem
+	}
+
+	if l.Front() == i && nextItem != nil {
+		l.head = nextItem
+	}
+
+	if l.Back() == i && prevItem != nil {
+		l.tail = prevItem
+	}
+
+	l.size--
+}
+
+func (l *list) MoveToFront(i *ListItem) {
+	l.Remove(i)
+	l.PushFront(i.Value)
 }
 
 func NewList() List {