PHP complete example of using ring-linked list to solve Joseph's problem

/**
  * Linked list structure
  */
class Child{
  public $no;
  public $next=null;
  public function __construct($no=null){
    $this->no = $no;
  }
}
/**
  * Linked List Operation
  */
class CycleLink{
  private $nodeNum = 0;
  /**
    * Add node
    */
  public function addNode($head,$node)
  {
    $currentNode = $head;
    while ($currentNode->next!=null && $currentNode->next!=$head) {
      $currentNode = $currentNode->next;
    }
    $currentNode->next = $node;
    $currentNode->next->next = $head;
    $this->nodeNum++;
  }
  /**
    * Delete nodes
    */
  public function delNode($head,$no)
  {
    $currentNode = $head;
    while ($currentNode->next!=$head) {
      if($currentNode->next->no==$no){
        $currentNode->next = $currentNode->next->next;
        $this->nodeNum--;
        break;
      }
      $currentNode = $currentNode->next;
    }
  }
  /**
    * Get the number of nodes
    */
  public function getNodeNum(){
    return $this->nodeNum;
  }
  /**
    * Find nodes
    */
  public function findNode($head,$no){
    $node = null;
    $currentNode = $head;
    while ($currentNode->next!=$head) {
      if($currentNode->next->no==$no){
        $node = $currentNode->next;
        break;
      }
      $currentNode = $currentNode->next;
    }
    return $node;
  }
  public function getNextNode($head,$node){
    if($node->next==$head){
      return $node->next->next;
    }
    return $node->next;
  }
  /**
    * Display node
    */
  public function showNode($head)
  {
    echo "<br/><br/>";
    $currentNode = $head;
    while ($currentNode->next!=$head){
      $currentNode = $currentNode->next;
      echo 'Part '.$currentNode-&gt;no.'A child<br/>';
    }
  }
}
/*
 //Create a head head, the head is just a header, and does not put data in
 $head = new Child();
 $childList = new CycleLink();
 $child_1 = new Child(1);
 $child_2 = new Child(2);
 $child_3 = new Child(3);
 $child_4 = new Child(4);
 $childList->addNode($head,$child_1);
 $childList->addNode($head,$child_2);
 $childList->addNode($head,$child_3);
 $childList->addNode($head,$child_4);
 $childList->showNode($head);
 echo "<pre>";
 var_dump($head);
 $findNode = $childList->findNode($head,3);
 echo "<pre>";
 var_dump($findNode);
 $childList->delNode($head,2);
 $childList->showNode($head);
 echo $childList->getNodeNum();
 exit();
 */
/**
  * Joseph's question
  * Suppose n people with numbers 1, 2,...n sit in a circle, and the person with number k (1<=k<=n) starts to count from 1, and the person with number m is out of the list.
  * Its next one starts to count from 1, the person who counts to m is delisted again, and so on, until everyone is delisted, thus generating a sequence of dequeue numbers.
  * And find out which person is the last one to be listed?
  */
class Josephu{
  private $head;
  private $childList;
  private $k;
  private $m;
  private $n;
  public function __construct($n,$k,$m){
    $this-&gt;k = $k;
    $this-&gt;m = $m;
    $this-&gt;n = $n;
    $this-&gt;createList($n);  // Create a child    echo "&lt;br/&gt;&lt;br/&gt;Currently there {$n} A little kid，From {$k} A little kid开始报数，Count to {$m} quit&lt;br/&gt;&lt;br/&gt;";
  }
  // Count  public function exec(){
    $currentNode = $this-&gt;childList-&gt;findNode($this-&gt;head,$this-&gt;k);  // Get the first person to start counting    $_num = 0;  // The value currently reached    $surplus_num = $this-&gt;n;
    // Start counting    while ($surplus_num&gt;1) {  // As long as the number of people is greater than 1, continue to report the number      // Current value      $_num++;
      $nextNode = $this-&gt;childList-&gt;getNextNode($this-&gt;head,$currentNode);
      // Count to mth number and remove it.  The report count returns to 0 and re-cycle.      if( $_num==$this-&gt;m ){
        $_num = 0;
        $surplus_num--;
        // The current child quits        $this-&gt;childList-&gt;delNode($this-&gt;head,$currentNode-&gt;no);
        echo '<br/>Exit child number:' . $currentNode-&gt;no;
      }
      // Move to the next child      $currentNode = $nextNode;
    }
    echo '<br/>The last child number:' . $currentNode-&gt;no;
  }
  // Create a child  private function createList($n){
    $this-&gt;childList = new CycleLink();
    $this-&gt;head = new Child();
    for ($i=1;$i&lt;=$n;$i++){
      $node = new Child($i);
      $this-&gt;childList-&gt;addNode($this-&gt;head,$node);
    }
    $this-&gt;childList-&gt;showNode($this-&gt;head);
  }
}
$josephu = new Josephu(4, 1, 2);
$josephu-&gt;exec();