[160]Intersection of Two Linked Lists

Write a program to find the node at which the intersection of two singly linked lists begins.

For example, the following two linked lists:

A: a1 → a2 ↘ c1 → c2 → c3 ↗
B: b1 → b2 → b3 begin to intersect at node c1.

Notes:

If the two linked lists have no intersection at all, return null. The linked lists must retain their original structure after the function returns. You may assume there are no cycles anywhere in the entire linked structure. Your code should preferably run in O(n) time and use only O(1) memory.

Code

Python

class Solution(object):
    def getIntersectionNode(self, headA, headB):
        if headA == None or headB == None:
            return None
        node1 = headA
        node2 = headB
        while node1 != node2:
            node1 = headB if node1 == None else node1.next
            node2 = headA if node2 == None else node2.next
        return node1