Explanation of PHP printing linked list example from end to end

topic

Enter a linked list and print the value of each node of the linked list from the end to the beginning.

Question explanation

One is to use the stack.
The second type is recursion.

Code

//Recursive versionfunction printListFromTailToHead($head)
{
  if($head == NULL){
    return [];
  }

  $arr = array();
  $cur = $head;

  if($cur-&gt;next != null){
    $arr = printListFromTailToHead($cur-&gt;next);  
  }
  array_push($arr, $cur-&gt;val);
  return $arr;



}
//Non-recursive versionfunction printListFromTailToHead($head)
{
  if($head == NULL){
    return [];
  }

  $cur = $head;
  $arr = array();
  $re = array();

  while($cur != NULL){
    array_push($arr, $cur-&gt;val);
    $cur = $cur -&gt;next;
  }


  while(!empty($arr)){
    $tmp = array_pop($arr);
    array_push($re, $tmp);
  }
  return $re;
}