feat: solve problem 146

medium/146. LRU Cache.go

@@ -0,0 +1,85 @@
+package medium
+
+type LRUNode struct {
+	Key, Val   int
+	Next, Prev *LRUNode
+}
+
+type LRUCache struct {
+	hash       map[int]*LRUNode
+	head, tail *LRUNode
+	cap        int
+	len        int
+}
+
+func ConstructorLRU(capacity int) LRUCache {
+	head, tail := &LRUNode{}, &LRUNode{}
+
+	head.Next = tail
+	tail.Prev = head
+	return LRUCache{
+		hash: make(map[int]*LRUNode, capacity),
+		head: head,
+		tail: tail,
+		cap:  capacity,
+		len:  0,
+	}
+}
+
+func (c *LRUCache) Get(key int) int {
+	v, ok := c.hash[key]
+	if !ok {
+		return -1
+	}
+
+	c.MoveNodeToTop(v)
+
+	return v.Val
+}
+
+func (c *LRUCache) MoveNodeToTop(node *LRUNode) {
+	if node == c.head.Next {
+		return
+	}
+	node.Prev.Next = node.Next
+	node.Next.Prev = node.Prev
+
+	first := c.head.Next
+	node.Next = first
+	node.Prev = c.head
+	c.head.Next = node
+	first.Prev = node
+}
+
+func (c *LRUCache) AddNodeToTop(node *LRUNode) {
+	node.Next = c.head.Next
+	node.Prev = c.head
+	c.head.Next.Prev = node
+	c.head.Next = node
+}
+
+func (c *LRUCache) Put(key int, value int) {
+	if c.Get(key) != -1 {
+		c.head.Next.Val = value
+		return
+	}
+
+	if c.len >= c.cap {
+		delete(c.hash, c.tail.Prev.Key)
+		c.tail.Prev = c.tail.Prev.Prev
+		c.tail.Prev.Next = c.tail
+		c.len--
+	}
+
+	newNode := &LRUNode{Key: key, Val: value}
+	c.AddNodeToTop(newNode)
+	c.hash[key] = newNode
+	c.len++
+}
+
+/**
+ * Your LRUCache object will be instantiated and called as such:
+ * obj := Constructor(capacity);
+ * param_1 := obj.Get(key);
+ * obj.Put(key,value);
+ */