两个链表的第一个公共结点

题目描述
输入两个链表，找出它们的第一个公共结点。

思想：（1）借助栈
（2）先计算h1,h2的长度，让长的先走。

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def FindFirstCommonNode(self, pHead1, pHead2):
        # write code here
        len1,len2 = 0,0
        p1,p2 = pHead1, pHead2
        while p1 != None:
            len1 += 1
            p1 = p1.next
        while p2 != None:
            len2 += 1
            p2 = p2.next
        p1,p2 = pHead1, pHead2
        t = len1 - len2
        if t > 0:
            while t > 0:
                t -= 1
                p1 = p1.next
        if t < 0:
            t = -t
            while t > 0:
                t -= 1
                p2 = p2.next
        while p1 != p2:
            p1 = p1.next
            p2 = p2.next
        return p1