#include <iostream>
#include <vector>
#include <map>
#define RES_MAX 5
using namespace std;

struct list
{
    list *next = NULL;
    int k = 0;
};

class Mem
{
public:
    int get(int k)
    {
        if (memcache.find(k) != memcache.end())
        {
            // cache hit: update visit list
            for (list **node = &visit; *node; node = &((*node)->next))
            {
                if ((*node)->k == k)
                {
                    list *found = *node;
                    *node = (*node)->next;
                    found->next = visit;
                    visit = found;
                    break;
                }
            }
            return memcache.find(k)->second;
        }
        else
        {
            // cache miss:
            if (memcache.size() < RES_MAX)
            {
                // if cache available: update visit list; update memcache
                list *node = new list;
                node->k = k;
                node->next = visit;
                visit = node;
                memcache.emplace(k, 0);
            }
            else
            {
                // if cache full: swap out oldest memcache; rm oldest visit; update visit
                for (list **node = &visit; *node; node = &(*node)->next)
                {
                    if ((*node)->next == NULL)
                    {
                        memcache.erase(memcache.find((*node)->k));
                        delete *node;
                        *node = NULL;
                        memcache.emplace(k, 0);
                        break;
                    }
                }
                list *node = new list;
                node->k = k;
                node->next = visit;
                visit = node;
            }
            return 0;
        }
    }
    int set(int k, int v)
    {
        if (get(k) != v)
        {
            memcache.find(k)->second = v;
        }
        return memcache.find(k)->second;
    }
    void print()
    {
        for (const auto &byte : memcache)
        {
            cout << byte.first << ": " << byte.second << endl;
        }
        for (list *node = visit; node; node = node->next)
        {
            cout << " -> " << node->k;
        }
        cout << endl;
    }

private:
    map<int, int> memcache;
    list *visit = NULL;
};

int main()
{
    Mem mem;
    for (int i = 10; i > 0; i--)
    {
        mem.get(i);
    }
    for (int i = 4; i < 7; i++)
    {
        if (mem.set(i, i) != i)
        {
            cout << "insert " << i << " failed" << endl;
        }
    }
    mem.print();
}