设计链表

/*
 * This is a solution for implementing a singly linked list using Java Streams.
 * Note that Java Streams are not typically used for this type of problem, but we'll use them where applicable.
 */
import java.util.stream.IntStream;
class MyLinkedList {
    private class Node {
        int val;
        Node next;
        Node(int val) {
            this.val = val;
        }
    }
    private Node head;
    private int size;
    public MyLinkedList() {
        head = null;
        size = 0;
    }
    public int get(int index) {
        if (index < 0 || index >= size) {
            return -1;
        }
        Node[] node = {head};
        IntStream.range(0, index).forEach(i -> node[0] = node[0].next);
        return node[0].val;
    }
    public void addAtHead(int val) {
        Node newNode = new Node(val);
        newNode.next = head;
        head = newNode;
        size++;
    }
    public void addAtTail(int val) {
        Node newNode = new Node(val);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
        }
        size++;
    }
    public void addAtIndex(int index, int val) {
        if (index < 0 || index > size) {
            return;
        }
        if (index == 0) {
            addAtHead(val);
        } else {
            Node newNode = new Node(val);
            Node[] node = {head};
            IntStream.range(0, index - 1).forEach(i -> node[0] = node[0].next);
            newNode.next = node[0].next;
            node[0].next = newNode;
            size++;
        }
    }
    public void deleteAtIndex(int index) {
        if (index < 0 || index >= size) {
            return;
        }
        if (index == 0) {
            head = head.next;
        } else {
            Node[] node = {head};
            IntStream.range(0, index - 1).forEach(i -> node[0] = node[0].next);
            node[0].next = node[0].next.next;
        }
        size--;
    }
}