Python3 代码

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def findFirstCommonNode(self, headA, headB):
        """
        :type headA, headB: ListNode
        :rtype: ListNode
        """
        ha = headA
        hb = headB

        while True:
            if ha == hb:
                break

            if ha is None:
                ha = headB
            else:
                ha = ha.next

            if hb is None:
                hb = headA
            else:
                hb = hb.next

        return ha