public void Put(int key, int value)
{
if (cache.ContainsKey(key))
{
// update the value.
cache[key].value = value;
moveToHead(cache[key]);
}
else
{
DLinkedNode newNode = new DLinkedNode();
newNode.key = key;
newNode.value = value;
cache.Add(key, newNode);
addNode(newNode);
++size;
if (size > capacity)
{
// pop the tail
DLinkedNode tail = popTail();
cache.Remove(tail.key);
--size;
}
}
}
private DLinkedNode popTail()
{
//Pop the current tail.
DLinkedNode res = tail.prev;
removeNode(res);
return(res);
}
private void removeNode(DLinkedNode node)
{
// Remove an existing node from the linked list.
DLinkedNode prev = node.prev;
DLinkedNode next = node.next;
prev.next = next;
next.prev = prev;
}
private void addNode(DLinkedNode node)
{
//Always add the new node right after head.
node.prev = head;
node.next = head.next;
head.next.prev = node;
head.next = node;
}
public int Get(int key)
{
if (!cache.ContainsKey(key))
{
return(-1);
}
DLinkedNode node = cache[key];
moveToHead(node);
return(node.value);
}
public LRUCache(int capacity)
{
this.size = 0;
this.capacity = capacity;
head = new DLinkedNode();
// head.prev = null;
tail = new DLinkedNode();
// tail.next = null;
head.next = tail;
tail.prev = head;
}
private void moveToHead(DLinkedNode node)
{
// Move certain node in between to the head.
removeNode(node);
addNode(node);
}