Day24-LRU-Cache.cpp

class LRUCache {
public:
        list<pair<int, int>> items;
        unordered_map<int, list<pair<int, int>>::iterator> cache;
        int capacity;
    LRUCache(int capacity) {
        this->capacity = capacity;
    }
    
    int get(int key) {
        if (cache.find(key) == cache.end())
            return -1;
        items.splice(items.begin(), items, cache[key]);
        return cache[key]->second;
    }
    
    void put(int key, int value) {
  
        if (cache.find(key) == cache.end()) {
            if (items.size() == capacity) {
                cache.erase(items.back().first);
                items.pop_back();
            }
            items.push_front(make_pair(key, value));
            cache[key] = items.begin();
        } else {
            cache[key]->second = value;
            items.splice(items.begin(), items, cache[key]);
        }
    }
};

/**
 * Your LRUCache object will be instantiated and called as such:
 * LRUCache* obj = new LRUCache(capacity);
 * int param_1 = obj->get(key);
 * obj->put(key,value);
 */