Merge two sorted list

• https://leetcode.com/problems/merge-two-sorted-lists/submissions/

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    if (l1 == null) return l2;
    if (l2 == null) return l1;

    ListNode dummyHead = new ListNode(0);
    ListNode head = dummyHead;

    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 (l1 != null) head.next = l1;
    if (l2 != null) head.next = l2;

    return dummyHead.next;
}