const getIntersectionNode = function(headA, headB) {
    if (headA === null || headB === null) {
        return null
    }
    let pA = headA, pB = headB
    while (pA !== pB) {
        pA = pA === null ? headB : pA.next
        pB = pB === null ? headA : pB.next
    }
    return pA
}