public void Add(int key, int value)
{
// just need to update value and move it to the top
if (map.ContainsKey(key))
{
LRUNode node = map[key];
doubleLinkedList.RemoveNode(node);
node.Value = value;
doubleLinkedList.AddToTop(node);
}
else
{
// if cache is full, then remove the least recently used node
if (count == capacity)
{
LRUNode lru = doubleLinkedList.RemoveLRUNode(); // remove the node
map.Remove(lru.Key); // the move the key out of the dictionary
count--;
}
// add a new node on top
LRUNode node = new LRUNode(key, value);
doubleLinkedList.AddToTop(node);
map[key] = node;
count++;
}
}
public LRUNode RemoveLRUNode()
{
LRUNode target = Tail.Previous;
RemoveNode(target);
return(target);
}
public void RemoveNode(LRUNode node)
{
node.Previous.Next = node.Next;
node.Next.Previous = node.Previous;
node.Next = null;
node.Previous = null;
}
public void AddToTop(LRUNode node)
{
node.Next = Head.Next;
Head.Next.Previous = node;
node.Previous = Head;
Head.Next = node;
}
public LRUDoubleLinkedList()
{
Head = new LRUNode();
Tail = new LRUNode();
Head.Next = Tail;
Tail.Previous = Head;
}
// each time when access the node, we move it to the top
public int Get(int key)
{
if (!map.ContainsKey(key))
{
return(-1);
}
LRUNode node = map[key];
doubleLinkedList.RemoveNode(node); // Remove node out of the list
doubleLinkedList.AddToTop(node); // Add back it on the top
return(node.Value);
}