Create LRUCache.cc

Author: iphkwan

LRUCache.cc

@@ -0,0 +1,42 @@
+class LRUCache{
+public:
+    LRUCache(int capacity) {
+        _cache_map.clear();
+        _cache_list.clear();
+        _max_size = capacity;
+    }
+    
+    int get(int key) {
+        unordered_map<int, list<pair<int, int> >::iterator >::iterator p = _cache_map.find(key);
+        if (p != _cache_map.end()) {
+            //_cache_list.erase(p->second);
+            //_cache_list.push_front(pair<int, int>(key, ret));
+            _cache_list.splice(_cache_list.begin(), _cache_list, p->second);
+            p->second = _cache_list.begin();
+            return (p->second)->second;
+        }
+        return -1;
+    }
+    
+    void set(int key, int value) {
+        unordered_map<int, list<pair<int, int> >::iterator >::iterator p = _cache_map.find(key);
+        if (p != _cache_map.end()) {
+            //_cache_list.erase(p->second);
+            //_cache_list.push_front(pair<int, int>(key, value));
+            ((p->second))->second = value;
+            _cache_list.splice(_cache_list.begin(), _cache_list, p->second);
+            p->second = _cache_list.begin();
+        } else {
+            if (_cache_map.size() >= _max_size) {
+                _cache_map.erase(_cache_list.rbegin()->first);
+                _cache_list.pop_back();
+            }
+            _cache_list.push_front(pair<int, int>(key, value));
+            _cache_map[key] = _cache_list.begin();
+        }
+    }
+private:
+    unordered_map<int, list<pair<int, int> >::iterator > _cache_map; //key, _cache_list iterator
+    list<pair<int, int> > _cache_list; // KV pair container
+    int _max_size;
+};