Merge Two Sorted Lists

1public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
2    ListNode dummy = new ListNode(0);
3    ListNode current = dummy;
4
5    ListNode p = list1;
6    ListNode q = list2;
7
8    while (p != null && q != null) {
9        if (p.val <= q.val) {
10            current.next = p;
11            p = p.next;
12        } else {
13            current.next = q;
14            q = q.next;
15        }
16        current = current.next;
17    }
18
19    if (p != null) {
20        current.next = p;
21    } else {
22        current.next = q;
23    }
24
25    return dummy.next;
26}