【Leetocode | 001】146. LRU 缓存机制

146. LRU 缓存机制

1. 题解

 1 class LRUCache {
 2 public:
 3     LRUCache(int capacity) {
 4         cap = capacity;
 5     }
 6     
 7     int get(int key) {
 8         
 9         auto it = m.find(key);
10         if(it == m.end()) return -1;
11         
12         l.splice(l.begin(), l, it->second);
13         return it->second->second;
14     }
15     
16     void put(int key, int value) {
17         auto iter = m.find(key);
18         if(iter != m.end()) l.erase(iter->second);
19         l.push_front(make_pair(key, value));
20         m[key] = l.begin();
21         
22         if(m.size() > cap)
23         {
24             auto it = l.rbegin();
25             m.erase(it->first);
26             
27             l.pop_back();
28         }
29     }
30     private:
31     int cap;
32     list<pair<int, int>> l;
33     unordered_map<int, list<pair<int,int>>::iterator> m;      
34 };
35 
36 /**
37  * Your LRUCache object will be instantiated and called as such:
38  * LRUCache* obj = new LRUCache(capacity);
39  * int param_1 = obj->get(key);
40  * obj->put(key,value);
41  */