1public class MyLinkedList {
2
3    private class Node {
4        public int val;
5        public Node next;
6        public Node(int _val) { val = _val; }
7    }
8
9    private Node head;
10
11    public MyLinkedList() {
12        head = null;
13    }
14
15    public int Get(int index) {
16        Node current = head;
17        for (int i = 0; i < index && current != null; i++) {
18            current = current.next;
19        }
20        return current == null ? -1 : current.val;
21    }
22
23    public void AddAtHead(int val) {
24        Node node = new Node(val);
25        node.next = head;
26        head = node;
27    }
28
29    public void AddAtTail(int val) {
30        Node node = new Node(val);
31        if (head == null) {
32            head = node;
33        } else {
34            Node current = head;
35            while (current.next != null) {
36                current = current.next;
37            }
38            current.next = node;
39        }
40    }
41
42    public void AddAtIndex(int index, int val) {
43        if (index == 0) {
44            AddAtHead(val);
45            return;
46        }
47        Node current = head;
48        for (int i = 0; i < index - 1 && current != null; i++) {
49            current = current.next;
50        }
51        if (current != null) {
52            Node node = new Node(val);
53            node.next = current.next;
54            current.next = node;
55        }
56    }
57
58    public void DeleteAtIndex(int index) {
59        if (index == 0 && head != null) {
60            head = head.next;
61            return;
62        }
63        Node current = head;
64        for (int i = 0; i < index - 1 && current != null; i++) {
65            current = current.next;
66        }
67        if (current != null && current.next != null) {
68            current.next = current.next.next;
69        }
70    }
71}

1