0160.Intersection of Two Linked Lists

from typing import Optional

class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:
    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> Optional[ListNode]:
        a, b = headA, headB
        while a != b:
            a = a.next if a else headB
            b = b.next if b else headA
        return a

if __name__ == "__main__":
    # 构造相交链表
    c1 = ListNode(8)
    c2 = ListNode(4)
    c3 = ListNode(5)
    c1.next = c2
    c2.next = c3

    a1 = ListNode(4)
    a2 = ListNode(1)
    a1.next = a2
    a2.next = c1

    b1 = ListNode(5)
    b2 = ListNode(6)
    b3 = ListNode(1)
    b1.next = b2
    b2.next = b3
    b3.next = c1

    sol = Solution()
    res = sol.getIntersectionNode(a1, b1)
    print(res.val if res else None)