架构师训练营 - 第八周 - 作业

class Solution {
    /**
     * @param ListNode $headA
     * @param ListNode $headB
     * @return ListNode
     */
    function getIntersectionNode($headA, $headB) {
        if($headA == null || $headB == null){
            return null;
        }
        //先判断是否相交，不相交直接返回
        if(!$this->isIntersect($headA, $headB)){
            return null;
        }
        //若相交再找交叉点：分别遍历，并指向另一链表的头，这样遍历的长度相等
        $cura = $headA;
        $curb = $headB;
        while($cura || $curb){
            if($cura === $curb){
                break;
            }
            $cura = $cura == null ? $headB : $cura->next;
            $curb = $curb == null ? $headA : $curb->next;
        }
        return $cura;
    }

    //判断是否相交
    function isIntersect($headA, $headB){
        if($headB == null || $headB == null){
            return false;
        }
        while($headA->next != null){
            $headA = $headA->next;
        }
        while($headB->next != null){
            $headB = $headB->next;
        }
        return $headA === $headB;
    }
}