146.LRU Cache

//solution:
//easy
class LRUCache{
public:
    LRUCache(int capacity):capacity(capacity) {
    }
    
    int get(int key) {
        if(hash.find(key)==hash.end())
            return -1;
        else{
            nodeList.splice(nodeList.begin(),nodeList,hash[key]);
            hash[key]=nodeList.begin();
            return nodeList.begin()->value;
        }
        
        
    }
    
    void set(int key, int value) {
        if(hash.find(key)!=hash.end()){
            nodeList.splice(nodeList.begin(),nodeList,hash[key]);
            hash[key]=nodeList.begin();
            nodeList.begin()->value=value;
        }
        else{
            if(hash.size()<capacity){
                nodeList.push_front(node(key,value));
                hash[key]=nodeList.begin();
            }
            else{
                hash.erase(nodeList.back().key);
                nodeList.pop_back();
                nodeList.push_front(node(key,value));
                hash[key]=nodeList.begin();
            }
        }
        
    }
    int capacity;
    struct node{
        int key;
        int value;
        node(int key,int value):key(key),value(value){};
    };
    list<node> nodeList;
    unordered_map<int,list<node>::iterator> hash;
};