[해커랭크] Insert a node at the head of a linked list

문제링크: www.hackerrank.com/challenges/insert-a-node-at-the-head-of-a-linked-list/problem

Insert a node at the head of a linked list | HackerRank

다소 복잡한 리스트문제를 먼저 풀어서 그런지 이 문제는 1분안에 해결 되었다. 

새로운 노드를 head로 하고 원래 새로운 노드의 next를 이전 리스트에 연결했다

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    static class SinglyLinkedListNode {
        public int data;
        public SinglyLinkedListNode next;

        public SinglyLinkedListNode(int nodeData) {
            this.data = nodeData;
            this.next = null;
        }
    }

    static class SinglyLinkedList {
        public SinglyLinkedListNode head;
        public SinglyLinkedListNode tail;

        public SinglyLinkedList() {
            this.head = null;
            this.tail = null;
        }
      
    }

    public static void printSinglyLinkedList(SinglyLinkedListNode node, String sep, BufferedWriter bufferedWriter) throws IOException {
        while (node != null) {
            bufferedWriter.write(String.valueOf(node.data));

            node = node.next;

            if (node != null) {
                bufferedWriter.write(sep);
            }
        }
    }

    // Complete the insertNodeAtHead function below.

    /*
     * For your reference:
     *
     * SinglyLinkedListNode {
     *     int data;
     *     SinglyLinkedListNode next;
     * }
     *
     */
    static SinglyLinkedListNode insertNodeAtHead(SinglyLinkedListNode llist, int data) {
        SinglyLinkedListNode newNode = new SinglyLinkedListNode(data);
        if(llist ==null){
            return newNode;
        }
        newNode.next = llist;
        return newNode;

    }

    private static final Scanner scanner = new Scanner(System.in);