LeetCode Design

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class DoubleListNode {
public:
    int key;
    int value;
    DoubleListNode* next;
    DoubleListNode* prev;
    DoubleListNode(int k, int val) {
        key = k;
        value = val;
        next = nullptr;
        prev = nullptr;
    }
};

class LRUCache {
public:
    unordered_map<int, DoubleListNode*> dict;
    DoubleListNode* head;
    DoubleListNode* tail;

    int cap;
    int size;

    LRUCache(int capacity) {
        cap = capacity;
        size = 0;

        head = new DoubleListNode(-1, -1);
        tail = new DoubleListNode(-1, -1);

        head->next = tail;
        tail->prev = head;
    }

    int get(int key) {
        if (dict.count(key)) {
            DoubleListNode* node = dict[key];
            moveNodeToHead(node);
            return node->value;
        }
        return -1;
    }

    void put(int key, int value) {
        if (dict.count(key)) {
            DoubleListNode* node = dict[key];
            node->value = value;
            moveNodeToHead(node);
        } else {
            DoubleListNode* newNode = new DoubleListNode(key, value);
            insertHead(newNode);
            dict[key] = newNode;
            size++;

            if (size > cap) {
                DoubleListNode* node = tail->prev;

                removeNode(node);
                dict.erase(node->key);
                delete node;
                size--;
            }
        }
    }

    void moveNodeToHead(DoubleListNode* node) {
        removeNode(node);
        insertHead(node);
    }

    void removeNode(DoubleListNode* node) {
        DoubleListNode* prev = node->prev;
        DoubleListNode* next = node->next;

        prev->next = next;
        next->prev = prev;
    }

    void insertHead(DoubleListNode* newNode) {
        DoubleListNode* next = head->next;
        newNode->prev = head;
        head->next = newNode;
        newNode->next = next;
        next->prev = newNode;
    }

};

/**
 * Your LRUCache object will be instantiated and called as such:
 * LRUCache* obj = new LRUCache(capacity);
 * int param_1 = obj->get(key);
 * obj->put(key,value);
 */