Binary Tree in Javascript

Question

I'm working on this assignment: http://www.cs.colostate.edu/~anderson/ct310/index.html/doku.php?id=assignments:assignment_2

I'm building a binary tree in Javascript. Basically it's a relational tree, we have this tree class that takes 3 arguments: data,left child,right child. Left & right child are just new tree objects stored in var.

Here's the tree class:

function Tree( data, left, right ) 
{   
    // pravite data 
    var data = data; 
    var leftChild = left; 
    var rightChild = right; 

    // public functions 
    this.getData = function()
    {
        return data;
    }

    this.left = function()
    {
        return leftChild; 
    }

    this.right = function()
    {
        return rightChild; 
    }

}

Here's the toString() method

Tree.prototype.toString = function(indent) 
{
  var spaces = '';
  if (!indent)
  {
    indent = 0;
  }
  else{
    spaces = spaces*indent; 
  }
    // if the left tree isn't void
    if(this.tree().left())
    {
        this.tree().left().toString(indent+5); 
    }
    if(this.tree().right())
    {
        this.tree.right().toString(indent+5); 
    }
    print(spaces + this.data);
}

Here's the data I get passed into. We're using Rhino in the command line to test.

var abc = new Tree('a', new Tree('b'), new Tree('c'));
abc.toString()

I get a stack over flow on the toString method. My professor says to use the this.Left() in the if statement because when you recurse it will fail when it's undefined.

Any ideas what's wrong?

did you mean: if(this.left()) -- without the this.tree()? There is no this.tree in the constructor :) — mfeineis
– mfeineis, Commented Feb 17, 2012 at 15:37
It's strange to me to call this class "tree" instead of "node" as tree is the name of the larger structure. I would call a structure composed of trees with two pointers a binary forest. ba-bum-ch. — nwellcome
– nwellcome, Commented Feb 17, 2012 at 15:49

Niet the Dark Absol · Accepted Answer · 2012-02-17 15:36:50Z

3

Well, your last reference to the right branch is missing some parentheses...

this.tree.right().toString(indent+5) // <-- right here

That asid, I don't see this.tree() defined anywhere. I think it should be this.left() and this.right() in all those places.

Also, for a slight optimisation, consider something like:

var l = this.left();
if( l) l.toString(indent+5);

This avoids an extra function call.

answered Feb 17, 2012 at 15:36

Niet the Dark Absol

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Comments

Sam I am says Reinstate Monica · Accepted Answer · 2012-02-17 20:45:03Z

1

Your recursive function has no base case. It will just keep going forever.

If your node doesn't have any children, than don't call ToString on them()

answered Feb 17, 2012 at 20:45

Sam I am says Reinstate Monica

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