剑指offer 52 两个链表的第一个公共结点

class Solution:
    def FindFirstCommonNode(self , pHead1 , pHead2 ):
        # write code here
        
        #如果任意一个链表为空，则返回空
        if pHead1 is None or pHead2 is None :
            return None
        
        p1 = pHead1
        p2 = pHead2
        
        #包含两个链表存在且不相交的情况，p1和p2都会为None
        while p1 != p2:
 
            if p1:
                p1 = p1.next
            else:
                p1 = pHead2
            
            if p2:
                p2 = p2.next
            else:
                p2 = pHead1
 
        return p1