Merge Two Sorted List

Question:

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

//********** Hints ************

Merge Sort

//*****************************

Solution:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode root = new ListNode(-1);
        
        ListNode head = root;
        
        
        while(l1!= null && l2!= null){
            if(l1.val < l2.val){
                head.next = l1;
                l1 = l1.next;
            }
            else {
                head.next = l2;
                l2 = l2.next;
            }
            head = head.next;
        }
        
        if(l2!= null){
            head.next = l2;
        }
        
        else if(l1!= null ){
            head.next = l1;
        }
        
        return root.next;
    }
}