Linear table of data structure--a single linked list of chained storage structures (PHP code implementation)

The <?php/** * * 1.  class Lnode is used as a new node when creating a single-linked list. The  * 2.  class singlelinklist is used to create a single-linked list and some operations on a single-linked list (instantiating this class is equivalent to creating an empty list)  * 3. createlisthead :  the creation of a single-linked list with $num data elements-head interpolation  * 4. CreateListTail:  creation of single-linked lists with $num data elements-the  * 5 of the tail interpolation method.  DestroyList:  destroy single-linked list  * 6. clearlist: Empty single-linked list  * 7. listempty: Determine if a single-linked list is empty  * 8. listlength: Returns the number of data elements in a single-linked list  * 9. getelem: Returns the data element for a specified position in a single linked list  * 10.  Locateelem: Finds the ordinal of a specified element in a single-linked list  * 11. priorelem: Gets the previous element of the specified element  * 12.  Nextelem: Gets the following element of the specified element  * 13. listinsert: Inserts a data element before the specified position  * 14. ListDelete:  Delete data elements at a specified location  * 15. ListTraverse:  traverse all data elements of a single linked list  * */class LNode{     public  $data;    public  $next;    public  Function __construct ($data =null) {        $This->data= $data;         $this->next=null;     }}class SingleLinkList{    public  $data;     public   $next;     public function __construct () {          $this->data=null;         $this->next=null;     }    //creation of a single-linked list with $num data elements-head interpolation     public  Function createlisthead ($num) {        for ($i =0; $i < $num; $i + +) {              $node =new lnode ();              $node->data=mt_rand (100,200);              $node->next= $this->next;              $this->next= $node;        }     }    //creation of a single-linked list with $num data elements--tail interpolation     public function  Createlisttail ($num) {         $tail = $this;         for ($i =0; $i < $num; $i + +) {              $node =new lnode ();             $ Node->data=mt_rand (100,200);             $tail- >next= $node;             $tail = $node;         }         $node->next=null ;     }    //destroy single-link list     public function  Destroylist () {        //$this equivalent to the head pointer, which points to the head node, $this->next equivalent to the first node          //need to assign $this to $that because $this cannot be used as a variable for assignment          $that =$ This;        while ($that) {              $node = $that->next;             unset ($that);             $that =$ node;        }    }    // Empty the single-linked list     public function clearlist () {          $p = $this->next;        while ($p) {              $node = $p->next;             unseT ($node);             $p = $node;         }         $this->next=null;     }    //determine if a single-linked list is empty     public function  Listempty () {        if ($this->next) {             return false;        } else{            return true;         }    }    //returns the number of data elements in a single linked list      public function listlength () {        $ count=0;//Initialize variable          $p = $this->next;         while ($p) {             $count ++;              $p = $p->next;        }         return  $count;    }     Returns the data element at the specified location     public function getelem ($pos) {          $count =1;         $p = $this->next;         while ($p  &&  $count < $pos) {              $count ++;              $p = $p->next;        }         if (! $p  | |   $pos < $count) {            return  ' ERROR ';         }        return   $p->data;    }//     or     public  FUNCTION&NBSP;GETELEM2 ($pos) {         $count =0;          $p = $this->next;        while ($p) {              $count ++;             if ($count = = $pos) {                 return  $p->data;             }            $ p= $p->next;        }         return  ' ERROR ';    }    //finds the ordinal of a specified element in a single-linked list     public function  locateelem ($elem) {         $count =0;          $p = $this->next;        while ($p) {              $count ++;             if ($p->data== $elem) {                 return  $count;             }        }         return  ' ERROR ';     }    //gets the previous element of the specified element     public function priorelem ($elem) {          $p = $this-&GT;NEXT;&NBSP;&NBsp;      if ($p  &&  $p->data= $elem) {             return  $p->data. ' is already the first element, no precursor element ';        }         while ($p  &&  $p->next) {              $q = $p->next;            if ($q data== $elem) {                 return  $p->data;            }              $p = $q;         }        return  ' ERROR ';    }     //gets the following element of the specified element     puBlic function nextelem ($elem) {         $p = $this->next;         while ($p  &&  $p->next) {             if ($p->data== $elem) {                 return  $p->next->data;             }              $p = $p->next;        }         if ($p  &&  $p->next==null) {             return  $p->data. ' is already the last element, no successor ';        }         return  ' ERROR ';     }    //inserts a node element     public function listinsert ($pos, $node) before the specified location {          $p = $this;         $count =0;         while ($p)  {              $count ++;            if   ($count  ==  $pos)  {                  $node->next =  $p->next;                  $p->next =  $node;                 return  ' OK ';             }              $p = $p->next;        }        return  ' ERROR ';     }    //or   the efficiency will be higher     public  function listinsert2 ($pos, $node) {         $p = $this;          $count =1;        while ($p  &&  $count < $pos) {             $count ++;             $p = $p->next;         }        if (! $p  | |   $count > $pos) {            return  ' ERROR ';        }         $node- >next= $p->next;         $p->next= $node;        return  ' OK ';     }    //delete the data element at the specified position of the single-linked list     public  Function listdelete ($pos) {         $count =1;          $p = $this;         while ($p  & &  $count < $pos) {             $count + +;              $p = $p->next;         }        if (! $p  | |   $count > $pos) {            return  ' ERROR ';        }         $q = $p- >next;         $p->next= $q->next;        unset ($q);         return  ' OK ';    }//     or      public function listdelete2 ($pos) {         $count =0;         $p = $this;         //Here the reason for using $p->next rather than $p as a condition is that it can be less of a meaningless loop when the list is empty.         while ($p->next) {              $count ++;             if ($count = = $pos) {                  $q = $p->next;                  $p->next= $q->next;      &Nbsp;         unset ($q);                 return  ' OK ';             }              $p = $p->next;        }         return  ' ERROR ';     }    //single-linked list traversal      public function listtraverse () {         $arr =array ();          $p = $this->next;         while ($p) {             $arr []= $p->data;              $p = $p->next;         }        return  $arr;     }} 

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Linear table of data structure--a single linked list of chained storage structures (PHP code implementation)