private void MoveToHead(LRUCacheNode node)
{
_head.Prev = node;
node.Next = _head;
node.Prev = null;
_head = node;
}
public void Put(int key, int value)
{
if (_map.ContainsKey(key))
{
var node = _map[key];
node.Value = value;
if (_head == node)
{
return;
}
else if (node == _tail)
{
RemoveTail();
}
else
{
RemoveNode(node);
}
MoveToHead(node);
}
else
{
var node = new LRUCacheNode(key, value);
_map.Add(key, node);
if (_count == _capacity) // evicts
{
MoveToHead(node);
_map.Remove(_tail.Key);
RemoveTail();
}
else
{
if (_head == null) // count 0
{
_head = _tail = node;
}
else if (_head == _tail) // count 1
{
_tail.Prev = node;
node.Next = _tail;
_head = node;
}
else
{
MoveToHead(node);
}
_count++;
}
}
}
private void RemoveNode(LRUCacheNode node)
{
var prev = node.Prev;
var next = node.Next;
if (prev != null)
{
prev.Next = next;
}
if (next != null)
{
next.Prev = prev;
}
}
private void RemoveTail()
{
_tail = _tail.Prev;
_tail.Next = null;
}
