php链表笔记：合并两个有序链表

<?php
/**
 * Created by PhpStorm.
 * User: huizhou
 * Date: 2018/12/2
 * Time: 15:29
 */

/**
 * 合并两个有序链表
 * 思路:简单的合并排序。由于链表本来就是递增的，所以每次将两个链表中较小的部分拿过来就可以了。
 */

class MergeNode{
    private $next;
    private $value;

    public function __construct($value = null)
    {
        $this->value = $value;
    }

    public function getValue(){
        return $this->value;
    }

    public function setValue($value){
        $this->value = $value;
    }

    public function getNext(){
        return $this->next;
    }

    public function setNext($next){
        $this->next = $next;
    }

}

function test(){

    // 创建两个有序的链表

    $linkList=new MergeNode();

    $linkList->setNext(null);

    $temp=$linkList;

    for($i=1;$i<=10;$i+=2){

        $node=new MergeNode();

        $node->setValue($i);

        $node->setNext(null);

        $temp->setNext($node);

        $temp=$node;

    }

    //第二个有序的链表
    $list2=new MergeNode();

    $temp=$list2;

    for($i=2;$i<=10;$i+=2){

        $node=new MergeNode();

        $node->setValue($i);

        $node->setNext(null);

        $temp->setNext($node);

        $temp=$node;

    }

    $result = Merge($linkList,$list2);

    while($result != null){
        if($result->getValue()){
            echo  $result->getValue() .",";
        }
        $result = $result->getNext();
    }

}

test();

/**
 * 合并两个有序链表
 * @param MergeNode $pHead1
 * @param MergeNode $pHead2
 * @return MergeNode
 */
function Merge(MergeNode $pHead1,MergeNode $pHead2){

    if($pHead1 == null){
        return $pHead2;
    }

    if($pHead2 == null){
        return $pHead1;
    }

    if($pHead1->getValue() < $pHead2->getValue()){
        $resultHead = $pHead1;
        $pHead1 = $pHead1->getNext();
    }else{
        $resultHead = $pHead2;
        $pHead2 = $pHead2->getNext();
    }

    $pre = $resultHead;
    while ($pHead1 && $pHead2){

        if($pHead1->getValue() <= $pHead2->getValue()){
            $pre->setNext($pHead1);
            $pHead1 = $pHead1->getNext();
            $pre = $pre->getNext();
        }else{
            $pre->setNext($pHead2);
            $pHead2 = $pHead2->getNext();
            $pre = $pre->getNext();
        }

    }

    if($pHead1 != null){
        $pre->setNext($pHead1);
    }

    if($pHead2 !=null){
        $pre->setNext($pHead2);
    }

    return $resultHead;

}