list

hw04_lru_cache/cache.go

@@ -1,5 +1,9 @@
 package hw04lrucache
 
+import (
+	"sync"
+)
+
 type Key string
 
 type Cache interface {
@@ -9,8 +13,7 @@ type Cache interface {
 }
 
 type lruCache struct {
-	Cache // Remove me after realization.
-
+	mu       sync.Mutex
 	capacity int
 	queue    List
 	items    map[Key]*ListItem
@@ -28,3 +31,57 @@ func NewCache(capacity int) Cache {
 		items:    make(map[Key]*ListItem, capacity),
 	}
 }
+
+func (cache lruCache) Set(key Key, value interface{}) bool {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	existedListItem, ok := cache.items[key]
+
+	if ok {
+		cache.queue.Remove(existedListItem)
+	} else {
+		length := cache.queue.Len()
+
+		if length == cache.capacity {
+			// remove the last item from the map and queue
+			lastItem := cache.queue.Back()
+			itemKey := lastItem.Value.(cacheItem).key
+			delete(cache.items, itemKey)
+			cache.queue.Remove(lastItem)
+		}
+	}
+
+	newListItem := cacheItem{key, value}
+	// add item to the front
+	cache.queue.PushFront(newListItem)
+	cache.items[key] = cache.queue.Front()
+
+	return ok
+}
+
+func (cache lruCache) Get(key Key) (interface{}, bool) {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	var result interface{}
+
+	value, ok := cache.items[key]
+
+	if ok {
+		cache.queue.MoveToFront(cache.items[key])
+		result = value.Value.(cacheItem).value
+	} else {
+		result = nil
+	}
+
+	return result, ok
+}
+
+func (cache *lruCache) Clear() {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	cache.queue = NewList()
+	cache.items = make(map[Key]*ListItem, cache.capacity)
+}

hw04_lru_cache/cache_test.go

@@ -49,8 +49,87 @@ func TestCache(t *testing.T) {
 		require.Nil(t, val)
 	})
 
-	t.Run("purge logic", func(t *testing.T) {
-		// Write me
+	t.Run("more elements then in cache", func(t *testing.T) {
+		c := NewCache(3)
+
+		c.Set("aaa", 100)
+		c.Set("bbb", 200)
+		c.Set("ccc", 300)
+		c.Set("ddd", 400)
+
+		val, ok := c.Get("aaa")
+		require.False(t, ok)
+		require.Nil(t, val)
+
+		val, ok = c.Get("bbb")
+		require.True(t, ok)
+		require.Equal(t, 200, val)
+
+		val, ok = c.Get("ccc")
+		require.True(t, ok)
+		require.Equal(t, 300, val)
+
+		val, ok = c.Get("ddd")
+		require.True(t, ok)
+		require.Equal(t, 400, val)
+	})
+
+	t.Run("more elements then in cache with get", func(t *testing.T) {
+		c := NewCache(3)
+
+		c.Set("aaa", 100)
+		c.Set("bbb", 200)
+		c.Set("ccc", 300)
+
+		c.Get("ccc")
+		c.Get("bbb")
+		c.Get("aaa")
+		c.Set("ddd", 400)
+
+		val, ok := c.Get("aaa")
+		require.True(t, ok)
+		require.Equal(t, 100, val)
+
+		val, ok = c.Get("bbb")
+		require.True(t, ok)
+		require.Equal(t, 200, val)
+
+		val, ok = c.Get("ccc")
+		require.False(t, ok)
+		require.Nil(t, val)
+
+		val, ok = c.Get("ddd")
+		require.True(t, ok)
+		require.Equal(t, 400, val)
+	})
+
+	t.Run("more elements then in cache with set", func(t *testing.T) {
+		c := NewCache(3)
+
+		c.Set("aaa", 100)
+		c.Set("bbb", 200)
+		c.Set("ccc", 300)
+
+		c.Set("ccc", 300)
+		c.Set("bbb", 200)
+		c.Set("aaa", 100)
+		c.Set("ddd", 400)
+
+		val, ok := c.Get("aaa")
+		require.True(t, ok)
+		require.Equal(t, 100, val)
+
+		val, ok = c.Get("bbb")
+		require.True(t, ok)
+		require.Equal(t, 200, val)
+
+		val, ok = c.Get("ccc")
+		require.False(t, ok)
+		require.Nil(t, val)
+
+		val, ok = c.Get("ddd")
+		require.True(t, ok)
+		require.Equal(t, 400, val)
 	})
 }
 

hw04_lru_cache/go.mod

@@ -1,10 +1,9 @@
-module github.com/fixme_my_friend/hw04_lru_cache
+module hw04_lru_cache
 
 go 1.16
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/stretchr/testify v1.7.0
-	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

hw04_lru_cache/go.sum

@@ -1,20 +1,13 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.5.0 h1:DMOzIV76tmoDNE9pX6RSN0aDtCYeCg5VueieJaAo1uw=
-github.com/stretchr/testify v1.5.0/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
-gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

hw04_lru_cache/list.go

@@ -1,5 +1,9 @@
 package hw04lrucache
 
+import (
+    "fmt"
+)
+
 type List interface {
 	Len() int
 	Front() *ListItem
@@ -8,6 +12,7 @@ type List interface {
 	PushBack(v interface{}) *ListItem
 	Remove(i *ListItem)
 	MoveToFront(i *ListItem)
+	Print()
 }
 
 type ListItem struct {
@@ -17,10 +22,123 @@ type ListItem struct {
 }
 
 type list struct {
-	List // Remove me after realization.
-	// Place your code here.
+	firstNode *ListItem
+	lastNode  *ListItem
+	len       int
 }
 
 func NewList() List {
 	return new(list)
 }
+
+func (l list) Len() int {
+	return l.len
+}
+
+func (l list) Front() *ListItem {
+	if l.len > 0 {
+		return l.firstNode
+	}
+	return nil
+}
+
+func (l list) Back() *ListItem {
+	if l.len > 0 {
+		return l.lastNode
+	}
+
+	return nil
+}
+
+func (l *list) PushFront(v interface{}) *ListItem {
+	newItem := ListItem{v, nil, nil}
+
+	l.len++
+
+	if l.len > 1 {
+		newItem.Next = l.Front()
+		l.firstNode.Prev = &newItem
+	}
+
+	l.firstNode = &newItem
+
+	if l.len == 1 {
+		l.lastNode = &newItem
+	}
+
+	return l.Front()
+}
+
+func (l *list) PushBack(v interface{}) *ListItem {
+	newItem := ListItem{v, nil, nil}
+
+	l.len++
+
+	if l.len > 1 {
+		newItem.Prev = l.Back()
+		l.lastNode.Next = &newItem
+	}
+
+	l.lastNode = &newItem
+
+	if l.len == 1 {
+		l.firstNode = &newItem
+	}
+
+	return l.Back()
+}
+
+func (l *list) Remove(i *ListItem) {
+	l.len--
+
+	if l.Front() == i {
+		l.firstNode = i.Next
+	}
+
+	if l.Back() == i {
+		l.lastNode = i.Prev
+	}
+
+	if i.Prev != nil {
+		i.Prev.Next = i.Next
+	}
+
+	if i.Next != nil {
+		i.Next.Prev = i.Prev
+	}
+}
+
+func (l *list) MoveToFront(i *ListItem) {
+	if l.Front() == i {
+		return
+	}
+
+	if i.Prev != nil {
+		i.Prev.Next = i.Next
+	}
+
+	if i.Next != nil {
+		i.Next.Prev = i.Prev
+	} else {
+		l.lastNode = i.Prev
+	}
+
+	i.Prev = nil
+	i.Next = l.Front()
+	l.Front().Prev = i
+	l.firstNode = i
+}
+
+func (l list) Print() {
+	if l.firstNode == nil {
+		fmt.Println(nil)
+		return
+	}
+
+	i := l.Front()
+
+	for i != nil {
+		fmt.Println(i.Value)
+		i = i.Next
+	}
+}