// remove target node from current frequency double-linked list,
// and then promote it to higher frequency double-linked list
private void PromoteNode(LFUNode node)
{
LFUDoubleLinkedList dll = frequencyMap[node.Frequency];
dll.RemoveNode(node);
if (dll.Count == 0)
{
frequencyMap.Remove(node.Frequency);
if (minFrequency == node.Frequency)
{
minFrequency++;
}
}
node.Frequency++;
if (!frequencyMap.ContainsKey(node.Frequency))
{
frequencyMap[node.Frequency] = new LFUDoubleLinkedList();
}
frequencyMap[node.Frequency].AddToTop(node);
}
public void Add(int key, int value)
{
if (capacity == 0)
{
return;
}
// update the value of that node and then promote the node
if (map.ContainsKey(key))
{
LFUNode node = map[key];
node.Value = value;
PromoteNode(node);
}
else
{
// remove the LFU node
if (count == capacity)
{
LFUDoubleLinkedList dll = frequencyMap[minFrequency];
LFUNode lfuNode = dll.RemoveLFUNode();
if (dll.Count == 0)
{
frequencyMap.Remove(minFrequency);
}
map.Remove(lfuNode.Key);
count--;
}
// add a new node
LFUNode node = new LFUNode(key, value);
minFrequency = node.Frequency;
map[key] = node;
if (!frequencyMap.ContainsKey(node.Frequency))
{
frequencyMap[node.Frequency] = new LFUDoubleLinkedList();
}
frequencyMap[node.Frequency].AddToTop(node);
count++;
}
}
