两个链表的第一个公共结点

 1 # -*- coding:utf-8 -*-
 2 # class ListNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 class Solution:
 7     def FindFirstCommonNode(self, pHead1, pHead2):
 8         # write code here
 9         if not pHead1 or not pHead2:
10             return None
11         # 分别计算两个链表的长度
12         n1 = 0
13         n2 = 0
14         p1 = pHead1
15         p2 = pHead2
16         while p1:
17             n1 += 1
18             p1 = p1.next
19         while p2:
20             n2 += 1
21             p2 = p2.next
22         #p1 = pHead1
23         #p2 = pHead2
24         if n1>n2: #第一个链表长，让第一个链表先走n步
25             n = n1 -n2
26             while n!= 0:
27                     n = n-1
28                     pHead1 = pHead1.next
29         else:
30             n = n2 -n1
31             while n!= 0:
32                     n = n-1
33                     pHead2 = pHead2.next
34         while pHead1 != pHead2 and pHead1 and pHead2:
35                 pHead1 = pHead1.next
36                 pHead2 = pHead2.next
37         if pHead1 == pHead2:
38             return pHead1
39         else:
40             return None
41