【Leetcode】LRU Cache

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.

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 should invalidate the least recently used item before inserting a new item.

双向链表 + hash map

class LRUCache{
public:
    LRUCache(int capacity) {
        this->capacity = capacity;
    }
    
    int get(int key) {
        if (cache_map.find(key) != cache_map.end()) {
            cache_list.splice(cache_list.begin(), cache_list, cache_map[key]);
            cache_map[key] = cache_list.begin();
            return cache_map[key]->value;
        } else {
            return -1;
        }
    }
    
    void set(int key, int value) {
        if (cache_map.find(key) != cache_map.end()) {
            cache_list.splice(cache_list.begin(), cache_list, cache_map[key]);
            cache_map[key] = cache_list.begin();
            cache_map[key]->value = value;
        } else {
            if (cache_list.size() == capacity) {
                cache_map.erase(cache_list.back().key);
                cache_list.pop_back();
            }
            cache_list.push_front(cacheNode(key, value));
            cache_map[key] = cache_list.begin();
        }
    }
private:
    struct cacheNode {
        int key;
        int value;
        cacheNode(int key, int value) : key(key), value(value) {}
    };
    
    int capacity;
    unordered_map<int, list<cacheNode>::iterator> cache_map;
    list<cacheNode> cache_list;
};