/
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode next;
* ListNode(int x) : val(x), next(NULL) {}
* };
/
class Solution {
public:
ListNode merge(ListNode l1, ListNode* l2) {
auto dummy = new ListNode(-1),tail = dummy;
while (l1 && l2)
if(l1->val < l2->val)
{
tail = tail->next = l1;
l1 = l1 ->next;
}
else
{
tail = tail->next = l2;
l2 = l2->next;
}
if(l1) tail->next = l1;
if(l2) tail->next = l2;
return dummy ->next;
}
};