Leetcode-160 intersecting linked list

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

class Solution(object):
    def getIntersectionNode(self, headA, headB):
        """
        :type head1, head1: ListNode
        :rtype: ListNode
        """
        p, q = headA, headB
        while not p == q:
            p = p.next if p else headB
            q = q.next if q else headA
        return p