yjiang's cake

<?php
class Node {
    public $data;
    public $next;
    public function __construct($data=null, $next=null){
        $this->data = $data;
        $this->next = $next;
    }
}

class Link {
    public $head=null;
    public $size=0;

    public function __construct(){
        //$this->head = new Node();
    }

    //遍历
    public function traverse(){
        //当前指针位置移动到头部
        $curIndex = $this->head;
        $tmp = [];
        //移动指针一直到没有数据位置
        while( !is_null($curIndex) ){
            array_push($tmp, $curIndex->data);
            //移动指针到当前的下一个节点
            $curIndex = $curIndex->next;
        }
        return $tmp;
    }

    //头插
    public function addAtHead($data){
        $node = new Node($data, $this->head);
        $this->head = $node;
        $this->size++;
        return $this;
    }

    //尾插
    public function addAtTail($data){
        $node = new Node($data);
        $curIndex = $this->head;
        //判断当前链表是否为空
        if( is_null($curIndex) ){
            $this->head = $node;
        }
        else{
            //如果链表不为空，则进行遍历
            while( !is_null($curIndex->next) ){
                $curIndex = $curIndex->next;
            }
            $curIndex->next = $node;
        }
        $this->size++;
        return $this;
    }

    public function addAtIndex($data, $index){
        //判断index是头尾的情况
        $count = $this->size;
        if( $index <= 0 ){
            $this->addAtHead($data);
        }
        if( $index > $count ){
            $this->addAtTail($data);
        }

        //将指针移动到index-1的位置
        $curIndex = $this->head;
        for($i=0;$i<$index-1;$i++){
            $curIndex = $curIndex->next;
        }

        //新建一个节点，其next是index之后的链表
        $node = new Node($data, $curIndex->next);
        $curIndex->next = $node;

        $this->size++;
        return $this;
    }

    public function delAtIndex($index){
        $count = $this->size;
        $curIndex = $this->head;
        //如果删除的是第一个节点
        if( $index == 0 ){
            $this->head = $curIndex->next;
            $this->size--;
            return $this;
        }
        //如果删除的是最后一个节点
        if( $index < 0 || $index > $count ){
            echo "没有这个节点\n";
            return $this;
        }

        //将指针移到index-1的位置
        for($i=0;$i<$index-1;$i++){
            $curIndex = $curIndex->next;
        }
        //echo "<pre>"; print_r($curIndex);exit;
        //此时，curIndex->next所处的位置，也就是index
        //将从index开始的链表赋给tmp(tmp所处的位置 = index+2)
        $tmp = $curIndex->next;

        //index+2后的链表赋值跟index
        $curIndex->next = $tmp->next;
        $this->size--;

        return $this;
    }

    public function print(){
        print_r( $this );
    }
}

$link = new Link;
$link->addAtHead(3)
     ->addAtHead(2)
     ->addAtHead(1)
     ->addAtTail(8)
     ->addAtTail(4)
     ->addAtTail(5)
     ->addAtIndex(10, 3)
     ->delAtIndex(2)
     ->print();
//$res = $link->traverse();
//$size = $link->size;
//echo "{$size}<pre>"; print_r($res);exit;