合并两个排序的链表

 1 # -*- coding:utf-8 -*-
 2 # class ListNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 class Solution:
 7     # 返回合并后列表
 8     def Merge(self, pHead1, pHead2):
 9         # write code here
10         if pHead1 is None:  #首先考虑极端的特殊情况
11             return pHead2
12         if pHead2 is None:
13             return pHead1
14         pMergeHead = None
15         if pHead1.val<pHead2.val:
16             pMergeHead = pHead1
17             pMergeHead.next = self.Merge(pHead1.next,pHead2) #这里递归的时候方法的调用依然要用类实例.方法，而类中的self就是指类实例
18         else:
19             pMergeHead = pHead2
20             pMergeHead.next = self.Merge(pHead2.next,pHead1) 
21         return pMergeHead   #递归的输出是两个链表排序合并后的列表的指针（就是这个链表）