Question

So in an interview, I was actually asked a simple question that goes like this, say that I have a nested JSON response, [a, b, c ,d [a, [b, [d, e], g], h]. I am asked to implement a class that basically can handle to store this data and a print method to do so, so here’s what I have:

public class JSONode
{
   private String str;
   private JSONode nodes;

   public JSONode (String a, ArrayList<String> n)
   {
        str = a;
        nodes = n;
   }
}

public class JSONResp
{
  private ArrayList<JSONode> arr;

  public JSONResp ()
  {
    arr = new ArrayList<JSONode>();
  }

  public boolean checkCircular(JSONode temp)
  {
    for (int i = 0; i < arr.size(); i++)
    {
        if (arr.get(i).nodes == temp)
            return true;
    }
    return false;
  }

  public void add (JSONode nd)
  {
    if (!checkCircular(nd))
    arr.add(nd);
  }

  public void recurseJSONode(JSONode)
  {
      if (!JSONode.node)
           System.out.print(JSONode.str);
      else {
          System.out.print(JSONode.str);
          recurseJSONode(JSONode.node);
      }
  }

  public void print()
  {
    for (int i = 0; i < arr.size(); i++)
       recurseJSONode(arr.get(i));
  }

  public static void main (String[] args) {
      JSONResp x = new JSONResp();
      x.add(new JSONode("a", null);
      x.add(new JSONode("b", null);
  }

}

Now he said that there will circular references issues when I print, in other words I have list A = [a, b, c, D] and D = [q, t, y, A]. So he said I’d have to prevent from adding D by using the checkCircular above. I made an attempt. Also just a node I know my recurseJSONode isn’t correct and so does the print, so looking for a suggestion to fix that as well.. I am just curious to this problem.

Answer 1

First of all it should be like

public class JSONode
{
   private String str;
   private ArrayList<JSONode> nodes;

   public JSONode (String a, ArrayList<JSONode> n)
   {
        str = a;
        nodes = n;
   }
}

You have to check recursivly, if the given node is part of the parent node and the parent of the parent and so on…

So more like

public static boolean checkCircular(JSONode temp)
  {
    if(temp == null){
       return false;
    }

    ArrayList<JSONode> pNodes = temp.getChildrens();

    for (int i = 0; i < nodes.size(); i++)
    {
        if (pNodes.get(i).getString().equals(temp.getString()))
            return true;
        if(checkCircular(temp))
            return true;
    }
    return false;
  }