<?php

class Node
{
 private $Data;//节点数据
 private $Next;//存储下个点对象

 public function __construct($data, $next)
 { $this->Data = $data; $this->Next = $next;
 }

 public function __set($name, $value)
 { if (isset($this->$name)) $this->$name = $value;
 }

 public function __get($name)
 { if (isset($this->$name)) return $this->$name; else
 return NULL;
 }
}

class LinkList
{
 private $head;//头节点
 private $len;

 /**
 * 初始化头节点
 */
 public function __construct()
 { $this->init();
 }

 public function setHead(Node $val)
 { $this->head = $val;
 }

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

 public function getLen()
 { return $this->len;
 }

 public function init()
 { $this->setHead(new Node(NULL, NULL)); $this->len = 0;
 }

 /**
 * 设置某位置节点的数据
 * @param int $index
 * @param $data
 * @return bool
 */
 public function set(int $index, $data)
 { $i = 1; $node = $this->getHead(); while ($node->Next !== NULL && $i <= $index) { $node = $node->Next; $i++;
 } $node->Data = $data; return TRUE;
 }

 /**
 * 获取某位置节点的数据
 * @param int $index
 * @return mixed
 */
 public function get(int $index)
 { $i = 1; $node = $this->getHead(); while ($node->Next !== NULL && $i <= $index) { $node = $node->Next; $i++;
 } return $node->Data;
 }

 /**
 * 在某位置处插入节点
 * @param $data
 * @param int $index
 * @return bool
 */
 public function insert($data, int $index = 0)
 { if ($index <= 0 || $index > $this->getLen()) return FALSE; $i = 1; $node = $this->getHead(); while ($node->Next !== NULL) { if ($index === $i) break; $node = $node->Next; $i++;
 } $node->Next = new Node($data, $node->Next); $this->len++; return TRUE;
 }

 /**
 * 删除某位置的节点
 * @param int $index
 * @return bool
 */
 public function delete(int $index)
 { if ($index <= 0 || $index > $this->getLen()) return FALSE; $i = 1; $node = $this->getHead(); while ($node->Next !== NULL) { if ($index === $i) break; $node = $node->Next; $i++;
 } $node->Next = $node->Next->Next; $this->len--; return TRUE;
 }
}