Leetcode—146. LRU 缓存【中等】（shared_ptr、unordered

Leetcode—146. LRU 缓存【中等】（shared_ptr、unordered_map、list）

2024每日刷题（143）

Leetcode—146. LRU 缓存

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先验知识

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list & unordered_map 实现代码

struct Node{int key;int value;Node(int key, int value): key(key), value(value) {}
};class LRUCache {
public:LRUCache(int capacity): m_capacity(capacity) {}int get(int key) {// 不存在const auto it = map.find(key);if(it == map.cend()) {return -1;}// 存在const auto& listIt = it->second;// 还需要更新在cache中的位置cache.splice(cache.begin(), cache, listIt);return listIt->value;}void put(int key, int value) {// 存在该元素if(const auto it = map.find(key); it != map.cend()) {const auto& listIt = it->second;// 需要更新map中的valuelistIt->value = value;// 把元素移到list前面cache.splice(cache.begin(), cache, listIt);return; }// 不存在的情况// 判断cache的内存够不够if(cache.size() == m_capacity) {// 拿到cache中最后元素const Node& lastIt = cache.back(); // erase掉map中这个元素map.erase(lastIt.key);// cache中需要pop_back()cache.pop_back();}// 添加新元素cache.emplace_front(key, value);map[key] = cache.begin();}
private:const int m_capacity;list<Node> cache;unordered_map<int, list<Node>::iterator> map;
};/*** 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);*/

运行结果

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unordered_map + shared_ptr 实现代码

struct Node{int key;int value;shared_ptr<Node> prev;shared_ptr<Node> next;Node(int key, int value): key(key), value(value) {}
};class LRUCache {
public:LRUCache(int capacity): m_capacity(capacity) {join(head, tail);}int get(int key) {const auto it = map.find(key);// 不存在if(it == map.cend()) {return -1;}// 存在shared_ptr<Node> &tarNode = it->second;// 更新其cache位置remove(tarNode);moveToHead(tarNode);return tarNode->value;}void put(int key, int value) {// 存在if(const auto it = map.find(key); it != map.cend()) {shared_ptr<Node>& node = it->second;// 更新值node->value = value;// 更新其所在cache的位置remove(node);moveToHead(node);return;}// 不存在// 先判断cache内存是否满if(map.size() == m_capacity) {// 拿到cache中最后元素shared_ptr<Node> lastNode = tail->prev;// 并删除cache中最后元素remove(lastNode);// 删除其在map中的位置map.erase(lastNode->key);}// cache中添加新元素moveToHead(make_shared<Node>(key, value));map[key] = head->next;}void join(shared_ptr<Node> node1, shared_ptr<Node> node2) {node1->next = node2;node2->prev = node1;}void remove(shared_ptr<Node> node) {join(node->prev, node->next);}void moveToHead(shared_ptr<Node> node) {join(node, head->next);join(head, node);}private:const int m_capacity;shared_ptr<Node> head = make_shared<Node>(-1, -1);shared_ptr<Node> tail = make_shared<Node>(-1, -1);unordered_map<int, shared_ptr<Node>> map;
};/*** 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);*/