public LRUCache(int capacity)
{
Capacity = capacity;
dic = new Dictionary <int, DllNode>(Capacity);
Head = null;
Tail = null;
}
//Insert or Update
public void Set(int key, int value)
{
DllNode n = null;
if (dic.ContainsKey(key))
{
n = dic[key];
RemoveKey(key);
}
n = new DllNode(key, value);
//Add it back to the head;
if (dic.Count == Capacity)
{
// Remove least recently used
bool b = RemoveKey(Tail.Key);
if (b)
{
dic.Add(key, n);
AddToFront(n);
}
}
else
{
dic.Add(key, n);
AddToFront(n);
}
}
public DllNode(int k, int v)
{
Key = k;
Value = v;
Next = null;
Prev = null;
}
public bool RemoveKey(int key)
{
if (!dic.ContainsKey(key))
{
return(false);
}
DllNode n = dic[key];
RemoveFromLinkedList(n);
dic.Remove(key);
return(true);
}
public int Get(int key)
{
if (!dic.ContainsKey(key))
{
return(-1);
}
DllNode n = dic[key];
if (n != Head)
{
RemoveFromLinkedList(n);
AddToFront(n);
}
return(n.Value);
}
private void AddToFront(DllNode n)
{
if (n == null)
{
return;
}
if (Head == null)
{
Head = n;
Tail = n;
}
else
{
Head.Prev = n;
n.Next = Head;
Head = n;
}
}
private void RemoveFromLinkedList(DllNode n)
{
if (n == null)
{
return;
}
if (n.Prev != null)
{
n.Prev.Next = n.Next;
}
if (n.Next != null)
{
n.Next.Prev = n.Prev;
}
if (n == Tail)
{
Tail = n.Prev;
}
if (n == Head)
{
Head = n.Next;
}
}