Merge Two Sorted Lists

题目：

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.

分析：

题目要求合并两个已排序的链表，这里指的是两个从小到大排好序的，合并完成的链表也是有序的，从小到大，这里需要注意，有的测试用例是输入了空的链表，这里需要判断一下。

Java解题：

public class ListNode {int val;ListNode next;ListNode(int x) { val = x; }}public ListNode mergeTwoLists(ListNode l1, ListNode l2) {if(l1==null)return l2;else if(l2==null)return l1;ListNode l = null;ListNode head = null;if(l1.val<l2.val){head=l=l1;l1=l1.next;}else{head=l=l2;l2=l2.next;}while(l1!=null&&l2!=null){if(l1.val<=l2.val){l.next=l1;l1=l1.next;}else{l.next=l2;l2=l2.next;}l=l.next;}if(l1==null){l.next=l2;}elsel.next=l1;return head;}