leetcode/src/s0146_lru_cache.cpp
Sainnhe Park bef47e10bf
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s0146
2023-03-18 08:42:14 +08:00

66 lines
1.6 KiB
C++

#include "s0146_lru_cache.hpp"
void LRUCache::moveToHead(CacheNode *node) {
// 如果是头部节点
if (node == head) return;
// 如果不是头部节点,但是是尾部节点
if (node == tail) tail = node->prev;
// 处理该节点的前后两个节点的指针
if (node->prev) node->prev->next = node->next;
if (node->next) node->next->prev = node->prev;
// 将该节点移动到头部
node->prev = nullptr;
node->next = head;
// 处理头部节点
head->prev = node;
head = node;
}
LRUCache::LRUCache(int capacity) {
this->capacity = capacity;
head = nullptr;
tail = nullptr;
map = std::unordered_map<int, CacheNode *>();
}
int LRUCache::get(int key) {
if (map.size() == 0) return -1;
if (map.count(key) == 0) return -1;
moveToHead(map[key]);
return map[key]->value;
}
void LRUCache::put(int key, int value) {
// 如果 key 已存在,则更新 value ,并将这个节点移动到头部
if (map.count(key) == 1) {
map[key]->value = value;
moveToHead(map[key]);
return;
}
// 否则创建该节点
CacheNode *newNode = (CacheNode *)malloc(sizeof(CacheNode));
newNode->value = value;
newNode->key = key;
newNode->next = head;
newNode->prev = nullptr;
// 处理头部节点
if (head) head->prev = newNode;
head = newNode;
// 处理尾部节点
if (map.size() == 0) tail = newNode;
// 更新哈希表
map[key] = newNode;
// 如果容量已满
if (map.size() > capacity) {
// 更新尾部节点
CacheNode *node = tail;
if (tail->prev) {
tail->prev->next = nullptr;
tail = tail->prev;
}
// 移除该节点
map.erase(node->key);
free(node);
}
}