Merge Two Sorted Lists

Description:

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.

Code:

 1  ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {

 2         if (!l1)

 3             return l2;

 4         else if (!l2)

 5             return l1;

 6         else

 7         {

 8             ListNode * head, *p, *q, *result;

 9             if (l1->val < l2->val)

10             {

11                 head = l1;

12                 p = l1->next;

13                 q = l2;

14             }

15             else

16             {

17                 head = l2;

18                 p = l1;

19                 q = l2->next;

20             }

21             result = head;

22             while (p&&q)

23             {

24                 if (p->val < q->val)

25                 {

26                     result->next = p;

27                     result = p;

28                     p = p->next;

29                 }

30                 else

31                 {

32                     result->next = q;

33                     result = q;

34                     q = q->next;

35                 }

36             }

37             result->next = (p==NULL)?q:p;

38              return head; 

39         }

40     }