#146 LRU cache

最新推荐文章于 2024-05-11 09:00:00 发布

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最新推荐文章于 2024-05-11 09:00:00 发布

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/dongfangchun/p/7724736.html

本文介绍了一种使用C++实现的LRU(Least Recently Used)缓存机制。该实现利用了unordered_map和list的数据结构来高效地进行插入、删除和查找操作。通过维护一个双端队列和两个哈希映射，可以快速定位到最近最少使用的元素并将其移除，以保持缓存大小不超过预设的最大容量。

class LRUCache {
private:
	std::unordered_map<int, int> mapData;
	std::unordered_map<int, std::list<int>::iterator> mapIndex;
	std::list<int> list;
	int maxSize;
public:
	LRUCache(int capacity) {
		maxSize = capacity;
	}

	int get(int key) {
		auto search = mapData.find(key);

		if (search != mapData.end()) {//find it
			auto pair_delete = mapIndex.find(key);
			list.erase(pair_delete->second);

            list.push_back(key);			
            pair_delete->second = std::prev(list.end());
			return search->second;
		}
		else {//not find
			return -1;
		}
	}

	void put(int key, int value) {
		auto search = mapData.find(key);
		if (search != mapData.end()) {//find it
			auto pair_delete = mapIndex.find(key);
			list.erase(pair_delete->second);

            list.push_back(key);
            pair_delete->second = std::prev(list.end());	
			search->second = value;

		}
		else {//not find
			  //push to list
			list.push_back(key);
			mapData[key] = value;
			mapIndex[key] = std::prev(list.end());

			//overflow
			this->removeLRU();
		}
	}
	void removeLRU() {
		if (list.size() > maxSize) {
			auto iterBegin = list.begin();
			mapData.erase(*iterBegin);
			mapIndex.erase(*iterBegin);
			list.pop_front();
		}

	}
};

转载于:https://www.cnblogs.com/dongfangchun/p/7724736.html