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.
题目很简单有很简短，实际上对于链表的题目很容易想到递归的方法。新建一个头节点，不断拿两个链表的节点比较，谁小就链接上去。然后那个链表往下跳一个节点，AC码如下：
public ListNode
mergeTwoLists(ListNode l1, ListNode l2) {
if(l1==
null)
return l2;
if(l2==
null)
return l1;
ListNode resultHead;
if(l1.val<l2.val){
resultHead=l1;
resultHead.next=mergeTwoLists(l1.next,l2);
}
else{
resultHead=l2;
resultHead.next=mergeTwoLists(l1,l2.next);
}
return resultHead;
}
