[Leetcode] LRU Cache

Design and implement a data structure for least recently used (LRU) cache. It shocould support the following operations:getAndset.

get(key)-Get the value (will always be positive) of the key if the key exists in the cache, otherwise return-1.
set(key, value)-Set or insert the value if the key is not already present. When the cache reached its capacity, it shocould invalidate the least recently used item before inserting a new item.

Two-way linked list + hash Map

 1 class LRUCache{ 2 public: 3     LRUCache(int capacity) { 4         this->capacity = capacity; 5     } 6      7     int get(int key) { 8         if (cache_map.find(key) != cache_map.end()) { 9             cache_list.splice(cache_list.begin(), cache_list, cache_map[key]);10             cache_map[key] = cache_list.begin();11             return cache_map[key]->value;12         } else {13             return -1;14         }15     }16     17     void set(int key, int value) {18         if (cache_map.find(key) != cache_map.end()) {19             cache_list.splice(cache_list.begin(), cache_list, cache_map[key]);20             cache_map[key] = cache_list.begin();21             cache_map[key]->value = value;22         } else {23             if (cache_list.size() == capacity) {24                 cache_map.erase(cache_list.back().key);25                 cache_list.pop_back();26             }27             cache_list.push_front(cacheNode(key, value));28             cache_map[key] = cache_list.begin();29         }30     }31 private:32     struct cacheNode {33         int key;34         int value;35         cacheNode(int key, int value) : key(key), value(value) {}36     };37     38     int capacity;39     unordered_map<int, list<cacheNode>::iterator> cache_map;40     list<cacheNode> cache_list;41 };

 

[Leetcode] LRU Cache