lrucache/lru.go

@@ -2,6 +2,68 @@
 
 package lrucache
 
-func New(cap int) Cache {
-	panic("implement me")
+import (
+	"container/list"
+)
+
+type cacheEntry struct {
+	key   int
+	value int
+}
+
+type lrucache struct {
+	cap           int
+	data          map[int]*list.Element
+	recentEntries *list.List
+}
+
+func (c *lrucache) isFull() bool {
+	return c.recentEntries.Len() == c.cap
+}
+
+func (c *lrucache) Get(key int) (int, bool) {
+	e, ok := c.data[key]
+	if !ok {
+		return 0, false
+	}
+	entry := c.recentEntries.Remove(e).(cacheEntry)
+	c.data[key] = c.recentEntries.PushBack(entry)
+	return entry.value, true
+}
+
+func (c *lrucache) Set(key int, value int) {
+	if c.cap == 0 {
+		return
+	}
+	e, ok := c.data[key]
+	if ok {
+		c.recentEntries.Remove(e)
+		c.data[key] = c.recentEntries.PushBack(cacheEntry{key, value})
+		return
+	}
+	if c.isFull() {
+		removed := c.recentEntries.Remove(c.recentEntries.Front()).(cacheEntry)
+		delete(c.data, removed.key)
+	}
+	c.data[key] = c.recentEntries.PushBack(cacheEntry{key, value})
+}
+
+func (c *lrucache) Range(f func(key, value int) bool) {
+	for e := c.recentEntries.Front(); e != nil; e = e.Next() {
+		entry := e.Value.(cacheEntry)
+		if !f(entry.key, entry.value) {
+			return
+		}
+	}
+}
+
+func (c *lrucache) Clear() {
+	for k := range c.data {
+		delete(c.data, k)
+	}
+	c.recentEntries.Init()
+}
+
+func New(cap int) Cache {
+	return &lrucache{cap, make(map[int]*list.Element), list.New()}
 }