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.
Example:
Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4
C++
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode* head;
ListNode* tail = new ListNode(0);
head = tail;
while(l1&&l2)
{
if(l1->val < l2->val)
{
tail->next = l1;
l1 = l1->next;
}
else
{
tail->next = l2;
l2 = l2->next;
}
tail = tail->next;
}
if(l1)tail->next = l1;
if(l2)tail->next = l2;
return head->next;
}