# 146 - LRU Cache
解法一 - Hash Table + doubly linked list
這題是擴展眼界題,邊聽影片邊做,可以看:https://www.youtube.com/watch?v=q1Njd3NWvlY
class LRUCache {
public:
LRUCache(int capacity) {
capacity_ = capacity;
}
int get(int key) {
const auto it = m_.find(key);
// Key not found, return -1
if(it == m_.cend()) {
return -1;
}
// Key found, get value and move to front
cache_.splice(cache_.begin(), cache_, it->second);
return it->second->second;
}
void put(int key, int value) {
const auto it = m_.find(key);
// Key found
if(it != m_.cend()) {
it->second->second= value;
cache_.splice(cache_.begin(), cache_, it->second);
return;
}
// Key not found
if(cache_.size() == capacity_) {
const auto& node = cache_.back();
m_.erase(node.first);
cache_.pop_back();
}
cache_.insert(cache_.begin(), make_pair(key, value));
m_[key] = cache_.begin();
}
private:
int capacity_;
list<pair<int, int>> cache_; // Store <key, list iterator>
unordered_map<int, list<pair<int, int>>::iterator> m_; // Store <key, value>
};
/**
* 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);
*/
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