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lru_cache.cpp
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92 lines (74 loc) · 1.77 KB
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class Node{
public:
int key;
int value;
Node* prev;
Node* next;
Node(int _key, int _value){
key = _key;
value = _value;
prev = nullptr;
next = nullptr;
}
};
class LRUCache {
public:
int capacity;
int size;
unordered_map<int, Node*> map;
Node* head;
Node* tail;
LRUCache(int _capacity) {
size = 0;
capacity = _capacity;
head = new Node(-1, -1);
tail = new Node(-1, -1);
head->next = tail;
tail->prev = head;
}
void move_to_head(Node* node){
if(node->prev)
node->prev->next = node->next;
if(node->next)
node->next->prev = node->prev;
node->next = head->next;
node->prev = head;
head->next->prev = node;
head->next = node;
}
int get(int key) {
if(map.count(key) == 0)
return -1;
Node* node = map[key];
move_to_head(node);
return node->value;
}
void remove_tail(){
Node* node = tail->prev;
node->prev->next = node->next;
node->next->prev = node->prev;
map.erase(node->key);
delete node;
}
void put(int key, int value) {
if(map.count(key) == 0){
Node* node = new Node(key, value);
map[key] = node;
move_to_head(node);
if(size == capacity)
remove_tail();
else
size++;
}else{
Node* node = map[key];
node->value = value;
move_to_head(node);
}
}
};
/**
* 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);
*/