PHP实现单链表翻转操作示例

<?php
/**
 * @file reverselink.php
 * @author showersun
 * @date 2016/03/01 10:33:25
 **/
class node{
  private $value;
  private $next;
  public function __construct($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 = $next;
  }
}
//遍历，将当前节点的下一个节点缓存后更改当前节点指针 
function reverse($head){
  if($head == null){
    return $head;
  }
  $pre = $head;//注意：对象的赋值
  $cur = $head->getnext();
  $next = null;
  while($cur != null){
    $next = $cur->getnext();
    $cur->setnext($pre);
    $pre = $cur;
    $cur = $next;
  }
  //将原链表的头节点的下一个节点置为null，再将反转后的头节点赋给head 
  $head->setnext(null);
  $head = $pre;
  return $head;
}
//递归，在反转当前节点之前先反转后续节点 
function reverse2($head){
  if (null == $head || null == $head->getnext()) {
    return $head;
  }
  $reversedhead = reverse2($head->getnext());
  $head->getnext()->setnext($head);
  $head->setnext(null);
  return $reversedhead;
}
function test(){
  $head = new node(0);
  $tmp = null;
  $cur = null;
  // 构造一个长度为10的链表，保存头节点对象head  
  for($i=1;$i<10;$i++){
    $tmp = new node($i);
    if($i == 1){
      $head->setnext($tmp);
    }else{
      $cur->setnext($tmp);
    }
    $cur = $tmp;
  }
  //print_r($head);exit;
  $tmphead = $head;
  while($tmphead != null){
    echo $tmphead->getvalue().' ';
    $tmphead = $tmphead->getnext();
  }
  echo "\n";
  //$head = reverse($head);
  $head = reverse2($head);
  while($head != null){
    echo $head->getvalue().' ';
    $head = $head->getnext();
  }
}
test();
?>

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