ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode tmp(0);
ListNode* p = &tmp;
while(l1&&l2)
{
if(l1->val < l2->val)
{
p->next = l1;
l1 = l1->next;
}
else
{
p->next = l2;
l2 = l2->next;
}
p = p->next;
}
if(l1)
p->next = l1;
if(l2)
p->next = l2;
return tmp.next;
}
