node insert/ rotate back

#include <iostream>
#include<map>
#include<sstream>

using namespace std;
struct node {
    node* prev;
    node* next;
    int val, key;
    node(node* prev=nullptr,node* next=nullptr,int key=NULL,int val=NULL)
        :prev{ prev }, next{ next }, val{ val }, key{ key } {}

};

struct cache {
    int cp;
    node* head;
    node* tail;
    map<int, node*> mp;

    cache(int capacity = NULL) : cp(capacity), head{ nullptr }, tail{ nullptr }{}

    void set(int key, int val) {
        auto f = mp.find(key);
        if (f != mp.end()) { mp[key]->val = val; moveToTail(mp[key]); }
        else if (mp.size() < cp) {
            if (!head) {
                head = new node(nullptr, nullptr, key, val);
                mp[key] = head;
            }
            else if (!tail) {
                tail = new node(head, head, key, val);
                head->next = tail;
                head->prev = tail;
                mp[key] = tail;
            }
            else {
                node* n = new node(tail, head, key, val);
                tail->next = n;
                tail = n;
                head->prev=n;
                mp[key] = n;
            }//probably need a scenario where cp is only 1... but im not doing it...
        }
        else { //capacity is reached....shift head to the rear
            auto f = mp.find(head->key);
            mp.erase(f);
            tail = head;
            head = tail->next;
            tail->key = key;
            tail->val = val;
            mp[key] = tail;
        }

    }

    void moveToTail(node* n) {
        if (n == tail) { return; }
        else if (n == head) {
            tail = head;
            head = tail->next;
        }
        else {
            n->prev->next = n->next; //removes itself from old positiion
            n->next->prev = n->prev;

            n->next = head; //inserts itself in new postion
            n->prev = tail;

            tail->next = n; //updates the nodes on both sides
            head->prev = n;

            tail = n; //updates the tail
        }
    }

    int get(int key) { //push newest hits to the back
        auto f = mp.find(key);
        if (f == mp.end()) { return -1; }
        moveToTail(mp[key]);
        return tail->val;
    }

    void printptrs() {
        for (auto& n : mp) {
            cout << " prev = " << n.second->prev << " current = " << n.second << " next = " << n.second->next << "\n";
        }
    }
    void printMap() {
        for (auto& m : mp) {
            cout << "key = " << m.first << " val = " << m.second->val << "\n";
        }
    }
    void printMapOrdered() {
        node* n = head;
        do {
            cout << "key = " << n->key << " val = " << n->val << "\n";
            n = n->next;
        } while (n != head);


    }

};



int main()
{
   stringstream ss;
    ss << "4 0 1 2 3 4 5 6 7 8 9"; //simple test case
    int n,k,v;
    ss >> n;

    cache c(n);

   while(ss>>k>>v){
       c.set(k, v);
//printptrs();

    }
   c.get(4);
   c.printMap();
cout << " \n\n";
   c.printMapOrdered();

}