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| import java.util.HashMap;
import java.util.Map;
public class LRUCache {
class Node {
int key;
int val;
Node prev;
Node next;
public Node(int key, int val) {
this.key = key;
this.val = val;
}
public Node() {
}
}
private Node head, tail;
private int size;
private int capacity;
private Map<Integer, Node> cache = new HashMap<>();
public LRUCache(int capacity) {
this.capacity = capacity;
this.size = 0;
head = new Node();
tail = new Node();
head.next = tail;
tail.prev = head;
}
public int get(int key) {
Node node = cache.get(key);
if (node == null) {
return -1;
}
moveToHead(node);
return node.val;
}
public void put(int key, int val) {
Node node = cache.get(key);
if (node == null) {
Node newNode = new Node(key, val);
cache.put(key, newNode);
addToHead(newNode);
size++;
if (size > capacity) {
Node res = removeTail();
cache.remove(res.key);
size--;
}
} else {
node.val = val;
moveToHead(node);
}
}
private void addToHead(Node node) {
node.prev = head;
node.next = head.next;
head.next.prev = node;
head.next = node;
}
private void removeNode(Node node) {
node.prev.next = node.next;
node.next.prev = node.prev;
}
private void moveToHead(Node node) {
removeNode(node);
addToHead(node);
}
private Node removeTail() {
Node tmp = tail.prev;
removeNode(tmp);
return tmp;
}
}
|