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.

Example: Input: 1->2->4, 1->3->4 Output: 1->1->2->3->4->4

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null) return l2;
        if(l2 == null) return l1;

        ListNode dummy = new ListNode(0);
        ListNode elong = dummy;
        while(l1 != null && l2 != null) {
            if(l1.val < l2.val) {
                elong.next = l1;
                l1 = l1.next;
            } else {
                elong.next = l2;
                l2 = l2.next;
            }
            elong = elong.next;
        }

        if(l1 != null) {
            elong.next = l1;
            elong = elong.next;
            l1 = l1.next;
        } else if (l2 != null) {
            elong.next = l2;
            elong = elong.next;
            l2 = l2.next;
        }
        return dummy.next;
    }
}