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.
AC代码：
class Solution(object): def mergeTwoLists(self, l1, l2): ret_list = current = ListNode(0) while l1 is not None and l2 is not None: if l1.val <= l2.val: current.next = l1 l1 = l1.next else: current.next = l2 l2 = l2.next current = current.next if l1 is not None: current.next = l1 if l2 is not None: current.next = l2 return ret_list.next
因为都是有序的链表，直接按照大小遍历即可。
原文：http://www.cnblogs.com/zhuifengjingling/p/5225872.html