由LeetCode的LRU Cache谈到操作系统中LRU算法

 1 class LRUCache{
 2 public:
 3     LRUCache(int capacity) {
 4         size = capacity;
 5     }
 6     int get(int key) {
 7         if(cacheMap.find(key)==cacheMap.end())
 8             return -1;
 9         cacheList.splice(cacheList.begin(),cacheList,cacheMap[key]);
10         cacheMap[key] = cacheList.begin();
11         return cacheMap[key]->second;
12     }
13     void set(int key, int value) {
14         if(cacheMap.find(key)!=cacheMap.end()){
15             cacheList.splice(cacheList.begin(),cacheList,cacheMap[key]);
16             cacheMap[key] = cacheList.begin();
17             cacheMap[key]->second = value;
18         }
19         else{
20             if(cacheList.size()==size){
21                 cacheMap.erase(cacheList.back().first);
22                 cacheList.pop_back();
23             }
24             cacheList.insert(cacheList.begin(),make_pair(key,value));
25             cacheMap[key] = cacheList.begin();
26         }
27     }
28 private:
29     int size;
30     list<pair<int,int>> cacheList;
31     map<int,list<pair<int,int>>::iterator> cacheMap;
32 };