1 struct Node { 2     int key, value; 3     Node(int k, int v) : key(k), value(v) {} 4 }; 5  6 class LRUCache{ 7 private: 8     int size; 9     list
     
       nlist;10     unordered_map
      
       ::iterator> nmap;11 public:12     LRUCache(int capacity) {13         size = capacity;14     }15     16     int get(int key) {17         if (nmap.find(key) != nmap.end()) {18             nlist.splice(nlist.begin(), nlist, nmap[key]);19             nmap[key] = nlist.begin();20             return nlist.begin()->value;21         }22         return -1;23     }24     25     void set(int key, int value) {26         if (nmap.find(key) == nmap.end()) {27             if (size == nlist.size()) {28                 nmap.erase(nlist.back().key);29                 nlist.pop_back();30             }31             nlist.push_front(Node(key, value));32             nmap[key] = nlist.begin();33         } else {34             nlist.splice(nlist.begin(), nlist, nmap[key]);35             nmap[key] = nlist.begin();36             nlist.begin()->value = value;37         }38     }39 };