札记之PHP实现合并两个有序链表

合并两个有序链表，思路很简单，类似合并两个数组，两两进行比较，依次找出小的元素放入新链表中；
示例 1：
输入：[1,3,5,7,9] [2,4,6,8,10]
输出：[1,2,3,4,5,6,7,8,9,10]
代码实现

class ListNode
{
    private $data;
    private $next;
    public function __construct(string $data)
    {
        $this->data = $data;
    }
    public function __get($var)
    {
        return $this->$var;
    }
    public function __set($var, $val)
    {
        return $this->$var = $val;
    }
}

class LinkedList
{
    private $head = NULL;
    private $length = 0;
    private $currentNode;

    public function insert(string $data = NULL)
    {
        $newNode = new ListNode($data);
        if ($this->head === NULL) {
            $this->head = &$newNode;
        } else {
            $currentNode = $this->head;
            while ($currentNode->next !== NULL) {
                $currentNode = $currentNode->next;
            }
            $currentNode->next = $newNode;
        }
        $this->length++;
        return true;
    }

    public function getList()
    {
        return $this->head;
    }

    public function setList($head)
    {
        $this->head = $head;
    }
    
    public function mergerSortedList($listA, $listB)
    {
        if ($listA == NULL) {
            return $listB;
        }
        if ($listB == NULL) {
            return $listA;
        }
        $pListA = $listA->head;
        $pListB = $listB->head;
       
        $newNode = new ListNode(0);
        $currentNode = $newNode;

        while ($pListA != NULL && $pListB != NULL) {
            if ($pListA->data <= $pListB->data) {
                $currentNode->next = $pListA;
                $pListA = $pListA->next;
            } else {
                $currentNode->next = $pListB;
                $pListB = $pListB->next;
            }
            $currentNode = $currentNode->next;
        }
        //没处理完的放后面
        if ($pListA == NULL) {
            $currentNode->next = $pListA;
        }
        if (!$pListB == NULL) {
            $currentNode->next = $pListB;
        }
        return $newNode;
    }

    public function display()
    {
        echo 'LinkList length: ' . $this->length . PHP_EOL;
        $currentNode = $this->head;
        while ($currentNode !== NULL) {
            echo $currentNode->data . PHP_EOL;
            $currentNode = $currentNode->next;
        }
    }
}

$listA = new LinkedList();
$listA->insert(1);
$listA->insert(3);
$listA->insert(5);
$listA->insert(7);
$listA->insert(9);

$listB = new LinkedList();
$listB->insert(2);
$listB->insert(4);
$listB->insert(6);
$listB->insert(8);
$listB->insert(10);

$mergeList = new LinkedList();
$list = $mergeList->mergerSortedList($listA, $listB);
$mergeList->setList($list);
$mergeList->display();
运行结果
