题解 | #牛群的优先级缓存#

struct DLinkedNode {
    int key {0};
    int value {0};
    DLinkedNode* prev;
    DLinkedNode* next;
    DLinkedNode () = default;
    DLinkedNode (int _key, int _value) : key(_key), value(_value),prev(nullptr), next(nullptr) {

    }

};
class LRUCache {
  private :
    unordered_map<int, DLinkedNode*> cache;
    DLinkedNode* head;
    DLinkedNode* tail;
    int size {0};
    int capacity;
public:
    LRUCache(int _capacity) : capacity(_capacity) {
        head = new DLinkedNode(0,0);
        tail = new DLinkedNode(0,0);
        head->next = tail;
        tail->next = head;
    }
    void addHead(DLinkedNode* node) {
        node->prev = head;
        node->next = head->next;
        head->next->prev = node;
        head->next = node;
    }
    void removeNode(DLinkedNode* node) {
        node->next->prev = node->prev;
        node->prev->next = node->next;
    }
    void moveToHead(DLinkedNode* node) {
        removeNode(node);
        addHead(node);
    }
    DLinkedNode* removeTail() {
        DLinkedNode* node = tail->prev;
        removeNode(node);
        return node;
    }
    int setPriority(int key, int value) {
        if (!cache.count(key)) {
            auto node = new DLinkedNode(key, value);
            cache[key] = node;
            addHead(node);
            size++;
            if (size > capacity) {
                DLinkedNode* remove = removeTail();
                cache.erase(remove->key);
                delete remove;
            }
        } else {
            auto node = cache[key];
            node->value = value;
            moveToHead(node);
        }
        return -2;
    }
    int getPriority(int key) {
        if (!cache.count(key) ) {
            return -1;
        }
        DLinkedNode* node = cache[key];
        moveToHead(node);
        return node->value;
    }
};
class Solution {

  private:
    LRUCache* lrucache;

  public:

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param operations string字符串vector
     * @param args int整型vector<vector<>>
     * @return int整型vector
     */
    vector<int> cowCacheOperations(vector<string>& operations,
                                   vector<vector<int> >& args) {
        // write code here
        vector<int> res;
        for (int i = 0; i < operations.size(); i++) {
            string operation = operations[i];
            if (operation == "CowCache") {
               lrucache = new LRUCache(args[i][0]);
               res.emplace_back(-2);
            } else if (operation == "setPriority") {
                lrucache->setPriority(args[i][0], args[i][1]);
                res.emplace_back(-2);
            } else {
                int tmp = lrucache->getPriority(args[i][0]);
                res.emplace_back(tmp);
            }
        }
        return res;
    }

};