LRU - DLL, C++ (gcc)

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#include<bits/stdc++.h>
using namespace std;

#define MAX 200005

struct node{
    int key;
    int value;
    node *next, *prev;
};
node nodePool[MAX];
int nodeCount;

struct LRU{
    node *head, *tail;
};

LRU lru;
map<int,node *> db;

int K;
int len;

node *getNode(int key, int value)
{
    node *newNode = &nodePool[nodeCount++];
    newNode->key = key; newNode->value = value;
    newNode->prev = newNode->next = NULL;
    return newNode;
}

void push(node *cur)
{
    if(lru.head == NULL)
        lru.head = lru.tail =  cur;
    else
    {
        cur->next = lru.head;
        lru.head->prev = cur;
        lru.head = cur;
    }
}
void remove(node *cur)
{
    if(cur==NULL)
        return ;
    if(lru.head and lru.head->key == cur->key)
    {
        lru.head = lru.head->next;
        if(lru.head)
            lru.head->prev = NULL;
        
    }
    if(lru.tail and lru.tail->key == cur->key)
    {
        lru.tail = lru.tail->prev;
        if(lru.tail)
            lru.tail->next = NULL;
        
    }
    if(cur->next)
        cur->next->prev = cur->prev;
    if(cur->prev)
        cur->prev->next = cur->next;
        
    cur->prev = cur->next = NULL;

}

// =====================================================================
void LRUCache(int cap)
{
    db.clear();
    lru.head = lru.tail = NULL;
    nodeCount = 0;
    K = cap;
    len = 0;
}

//Function to return value corresponding to the key.
int GET(int key)
{
    if(db.find(key) != db.end())
    {
        node *curNode = db[key];
        remove(curNode);
        push(curNode);
        return curNode->value;
    }
    return -1;
    
}

//Function for storing key-value pair.
void SET(int key, int value)
{
    if(db.find(key)!=db.end())
    {
        node *curNode = db[key];
        curNode->value = value;
        remove(curNode);
        push(curNode);
        
    }
    else
    {
        node *newNode = getNode(key,value);
        db[key] = newNode;
        
        if(len < K)
        {
            push(newNode);
            len+=1;
        }
        else
        {
            // remove tail node 
            node *lruNode = lru.tail;
            remove(lruNode);
            db.erase(lruNode->key);

// push the new node at front
            push(newNode);
        }
        
    }
}

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