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| struct DLinkedNode
{
int key, value;
DLinkedNode* prev;
DLinkedNode* next;
DLinkedNode() : key(0), value(0), prev(nullptr), next(nullptr){};
DLinkedNode(int _key, int _value) : key(_key), value(_value), prev(nullptr), next(nullptr){};
};
class LRUCache
{
private:
unordered_map<int, DLinkedNode*> cache;
int size, capacity;
DLinkedNode* head;
DLinkedNode* tail;
public:
LRUCache(int _capacity) : size(0), capacity(_capacity)
{
head = new DLinkedNode();
tail = new DLinkedNode();
head->next = tail;
tail->prev = head;
}
int get(int key)
{
if(!cache.count(key))
{
return -1;
}
DLinkedNode* node = cache[key];
moveToHead(node);
return node->value;
}
void put(int key, int value)
{
if(!cache.count(key))
{
DLinkedNode* node = new DLinkedNode(key, value);
cache[key] = node;
addToHead(node);
size++;
if(size > capacity)
{
DLinkedNode* remove = tail->prev;
cache.erase(remove->key);
removeTail();
size--;
delete remove;
}
}
else
{
DLinkedNode* node = cache[key];
node->value = value;
moveToHead(node);
}
}
void addToHead(DLinkedNode* node)
{
node->prev = head;
node->next = head->next;
head->next->prev = node;
head->next = node;
}
void removeNode(DLinkedNode* node)
{
node->next->prev = node->prev;
node->prev->next = node->next;
}
void moveToHead(DLinkedNode* node)
{
removeNode(node);
addToHead(node);
}
DLinkedNode* removeTail()
{
DLinkedNode* node = tail->prev;
removeNode(node);
return node;
}
};
|
