DITCH THE NOISE. master REAL ENGINEERING.

class LRUCache {
    int capacity;
    list<pair<int, int>> cache; // {key, val}
    unordered_map<int, list<pair<int, int>>::iterator> map;

public:
    LRUCache(int cap) : capacity(cap) {}

    int get(int key) {
        if (map.find(key) == map.end()) return -1;
        cache.splice(cache.begin(), cache, map[key]);
        return map[key]->second;
    }
};