【C++实现】LFU缓存

 

#include
#include
#include
using namespace std;

//调试用
//void printList(int obj)
//{
//	cout << obj << "\t";
//}
//void printFun(unordered_map> &obj)
//{
//	for (unordered_map>::iterator it = obj.begin(); it != obj.end(); it++)
//	{
//		cout << it->first << "\t";
//		for_each(it->second.begin(), it->second.end(), printList);
//		cout << endl;
//	}
//}

class LFUCache
{
public:
	LFUCache(int capacity)
	{
		this->capacity = capacity;
	}

	void set(int key, int value)
	{
		if (mapData.find(key) != mapData.end())
		{
			int tmp = mapData[key].second;
			mapData[key] = make_pair(value, tmp);
		}
		else
		{
			if (mapData.size() < capacity)
			{
				mapData.insert(make_pair(key, make_pair(value, 0)));
			}
			else
			{
				for (unordered_map>::iterator it = count_sort.begin(); it != count_sort.end(); it++)
				{
					if (!it->second.empty())
					{
						int topNum = it->second.front();
						it->second.pop_front();
						mapData.erase(topNum);
						mapData.insert(make_pair(key, make_pair(value, 0)));
						break;
					}
				}
			}
		}
		update(key);
	}

	int get(int key)
	{
		if (mapData.find(key) == mapData.end())
		{
			return -1;
		}
		update(key);
		return mapData[key].first;
	}

	//统一更新访问次数
	void update(int key)
	{
		list ::iterator it = find(count_sort[mapData[key].second].begin(), count_sort[mapData[key].second].end(), key);
		if (it != count_sort[mapData[key].second].end())
		{
			count_sort[mapData[key].second].erase(it);
		}
		mapData[key].second++;
		count_sort[mapData[key].second].push_back(key);
		//printFun(count_sort);
	}

private:
	unordered_map> count_sort;//frequency,key of mapData
	int capacity;
	unordered_map> mapData;//key,value,count
};




int main()
{
	LFUCache cache(3);
	cache.set(2, 2);
	cache.set(1, 1);
	cout << cache.get(2) <<",";
	cout << cache.get(1) << ",";
	cout << cache.get(2) << ",";
	cache.set(3, 3);
	cache.set(4, 4);
	cout << cache.get(3) << ",";
	cout << cache.get(2) << ",";
	cout << cache.get(1) << ",";
	cout << cache.get(4) << endl;


	//LFUCache cache(2);
	//cache.set(1, 1);
	//cache.set(2, 2);
	//cout << cache.get(1) << endl;       // 返回 1
	//cache.set(3, 3);    // 去除 key 2
	//cout << cache.get(2) << endl;       // 返回 -1 (未找到key 2)
	//cout << cache.get(3) << endl;       // 返回 3
	//cache.set(4, 4);    // 去除 key 1
	//cout << cache.get(1) << endl;       // 返回 -1 (未找到 key 1)
	//cout << cache.get(3) << endl;       // 返回 3
	//cout << cache.get(4) << endl;       // 返回 4
	
	system("pause");
	return 0;
}