1 /**
2 * Definition for singly-linked list.
3 * struct ListNode {
4 * int val;
5 * ListNode *next;
6 * ListNode(int x) : val(x), next(NULL) {}
7 * };
8 */
9 class Solution {
10 public:
11 ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
12 // Start typing your C/C++ solution below
13 // DO NOT write int main() function
14 ListNode *p = l1, *q = l2, dummy(-1);
15 ListNode *curr = &dummy;
16 while (p || q) {
17 int a = INT_MAX, b = INT_MAX;
18 if (p) {
19 a = p->val;
20 }
21 if (q) {
22 b = q->val;
23 }
24 if (a < b) {
25 curr->next = p;
26 p = p->next;
27 }
28 else {
29 curr->next = q;
30 q = q->next;
31 }
32 curr = curr->next;
33 }
34 return dummy.next;
35 }
36 };
