leetcode 146 LRU缓存机制

class LRUCache {
public:
    LRUCache(int capacity) {
        cap = capacity;
    }
    
    int get(int key) {
        auto it = map1.find(key);
        if(it == map1.end())
            return -1;
        list1.splice(list1.begin(), list1, it->second);
        return it->second->second;
    }
    
    void put(int key, int value) {
        auto it = map1.find(key);
        if(it != map1.end())
        {
            list1.erase(it->second);
        }
        if(list1.size() == cap)
        {
            int k = list1.rbegin()->first;
            list1.pop_back();
            map1.erase(k);
        }
        list1.push_front(make_pair(key, value));
        map1[key] = list1.begin();
    }
private:
    int cap;
    list<pair<int, int>> list1;
    unordered_map<int, list<pair<int, int>>::iterator> map1;
};

/**
 * 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);
 */