LRU Cache

PHOTO EMBED

Mon Sep 16 2024 06:35:11 GMT+0000 (Coordinated Universal Time)

Saved by @codestored #cpp 

class DLL
{
public:
    DLL *next;
    DLL *prev;
    int _value;
    int _key;

    DLL(int _key, int _value)
    {
        this->_key = _key;
        this->_value = _value;
        next = NULL;
        prev = NULL;
    }
};

class LRU
{
public:
    DLL *head;
    DLL *tail;
    int capacity;
    map<int, DLL *> location;

    LRU(int capacity)
    {
        this->capacity = capacity;
        head = new DLL(-1, -1);
        tail = new DLL(-1, -1);
        head->next = tail;
        tail->prev = head;
    }

    void deleteNode(int key)
    {
        DLL *cur = location[key];
        DLL *prev_node = cur->prev;
        DLL *next_node = cur->next;

        prev_node->next = next_node;
        next_node->prev = prev_node;
        location.erase(key);
    }

    void addNode(int key, int value)
    {
        DLL *new_node = new DLL(key, value);
        DLL *next_node = head->next;

        head->next = new_node;
        new_node->prev = head;
        new_node->next = next_node;
        next_node->prev = new_node;
        location[key] = new_node;
    }

    void putInCache(int key, int value)
    {
        // value is not already in cache
        if (location.find(key) == location.end())
        {
            addNode(key, value);
            if (location.size() > capacity)
            {
                deleteNode(tail->prev->_key);
            }
        }
        else
        {
            deleteNode(key);
            addNode(key, value);
        }
    }

    int getData(int key)
    {
        if (location.find(key) != location.end())
        {
            int val = location[key]->_value;
            deleteNode(key);
            addNode(key, val);
            return val;
        }
        return -1;
    }
};
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