trouble with recursion in php

Question

I cannot figure out why this function is not working. Evertime I try to make the recursive call all I get is an IE page with a cannot display error message. I left // by the lines that is causing me the trouble. I also tried the call without the $this-> and got an error function not recognized

private function insert($key, $current)    {     
    $newnode=new Node($key); 
    $parent=$this->root;
    if($this->root==null)  {  
        $this->root=$newnode;         
        return;   
    } else {
        if($newnode->data > $parent->data) {
            $parent=$parent->rightChild;
            $this->insert($key, $parent);//if I comment this line it 
                //work, but that make the function useless
        } else {
            echo "smaller ";
        }
    }
}

Possible duplicate of stackoverflow.com/questions/6005602/… (sorry, couldn't resist) — Phil
– Phil, Commented May 15, 2011 at 0:07
Is the recursion condition ever NOT met? In other words is $newnode->data > $parent->data always true? — Michael Berkowski
– Michael Berkowski, Commented May 15, 2011 at 0:07
@Phil I LOL'ed enough that my 4 year old came to see what was up. — Michael Berkowski
– Michael Berkowski, Commented May 15, 2011 at 0:08
Please put braces around both your if and else blocks. Leaving them out leads to confusion and possibly incorrect control flow — Phil
– Phil, Commented May 15, 2011 at 0:09

Phil · Accepted Answer · 2011-05-15 00:26:10Z

1

The error is obviously an infinite recursive loop.

This is most probably due to the fact that you never use the $current argument.

You're always comparing the $newnode->data against $this->root->data which if greater once, will always be greater.

Update

Here's how I'd change it

private function insert($key, $current = null)
{
    $newnode = new Node($key);
    $parent = null === $current ? $this->root : $current;
    if (null === $parent) {
        $this->root = $newnode;
        return;
    }
    if ($newnode->data > $parent->data) {
        // same as before from here

edited May 15, 2011 at 0:26

answered May 15, 2011 at 0:18

Phil

166k25 gold badges265 silver badges269 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

trouble with recursion in php

1 Answer 1

Update

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Update

Comments

Your Answer

Sign up or log in

Post as a guest

Related