LRU Cache

class cacheNode{
    public cacheNode prev, next;
    public int key, val;
    public cacheNode(int k, int v){
        key = k;
        val = v;
    }
}
public class LRUCache {
    private int size = 0;
    private int cap = 0;
    private cacheNode head, tail;
    private HashMap<Integer, cacheNode> hm;
    public LRUCache(int capacity) {
        cap = capacity;
        hm = new HashMap<>();
    }
    public int get(int key) {
        if(!hm.containsKey(key)){
            return -1;
        } else {
            cacheNode crt = hm.get(key);
            if(size == 1 || crt == head){
                return crt.val;
            }
            crt.prev.next = crt.next;
            if (crt!=tail){
                crt.next.prev = crt.prev;
            } else {
                tail = crt.prev;
            }
            crt.next = head;
            head.prev = crt;
            crt.prev = null;
            head = crt;
            return head.val;
        }
    }
    
    public void set(int key, int value) {
        if(get(key) == -1){
            cacheNode crt = new cacheNode(key, value);
            hm.put(key, crt);
            if (head == null){
                head = crt;
                tail = crt;
            } else {
                crt.next = head;
                head.prev = crt;
                head = crt;
            }
            if(size < cap){
                ++size;
            } else {
                hm.remove(tail.key);
                tail = tail.prev;
                tail.next = null;
            }
        } else {
            head.val = value;
        }
    }
}