Merge Two Sorted Lists

题目：

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

解答：

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    ListNode dummyHead = new ListNode(0);
    ListNode p = dummyHead;

    while(l1 != null && l2 != null) {
        if(l1.val < l2.val) {
            p.next = l1;
            l1 = l1.next;
        } else {
            p.next = l2;
            l2 = l2.next;
        }

        p = p.next;
    }

    if(l1 != null) {
        p.next = l1;
    }

    if(l2 != null) {
        p.next = l2;
    }

    return dummyHead.next
}