相交链表

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def solve():
    def getIntersectionNode(headA, headB):
        if not headA or not headB:
            return None
        pA, pB = headA, headB
        while pA != pB:
            pA = pA.next if pA else headB
            pB = pB.next if pB else headA
        return pA
    a1 = ListNode(4)
    a2 = ListNode(1)
    b1 = ListNode(5)
    b2 = ListNode(6)
    b3 = ListNode(1)
    c1 = ListNode(8)
    c2 = ListNode(4)
    c3 = ListNode(5)
    a1.next = a2
    a2.next = c1
    b1.next = b2
    b2.next = b3
    b3.next = c1
    c1.next = c2
    c2.next = c3
    result = getIntersectionNode(a1, b1)
    print(result.val if result else None)