Search Method for Binary Search Tree Only Returns First Match and Stops

Question

I am trying to search a BST for all of the nodes that contain a specific value, however when I call the search function it only returns the first match ( My test data def. has two nodes that should be returned). How do I adjust my code to get all of the values that match my criteria?

Here is my BST Search Function:

...
    private String search(String target, Node ptr)
    {
        ptr = root;
        if (ptr == null)
        {
            return null;
        }
    int compare = target.CompareTo(ptr.riskLevel.ToString());
        if (compare == 0)
        {
            return "Audit ID: " + ptr.auditID  + 
                "\n" + "Risk Level: " + ptr.riskLevel + 
                "\n" + "Scanner Found In: " + ptr.scanner + 
                "\n" + "Device Affected: " + ptr.boxName + 
                "\n" + "Description: " + ptr.description + "\n";
        }
        if (compare < 0)
        {
            return search(target, ptr.left);
        }
            return search(target, ptr.right);
        }
    public virtual String search(String target)
    {
        return search(target, root);
    }

This is my main(); where I call the search method:

while (true)
{
    ...
    Console.Writeline(bst.search("I"));
}

In other words, I'm trying to return all Nodes from bst that have a riskLevel of "I".

Here is my output (there should be two):

My BST contains the following methods:

• insert()
• search()
• displayAll()
• coutnNodes()
• save()

I'm happy to post the entire BST class if needed.

Answer 1

I was not traversing the tree properly.

I reused this preOrder method from a previous project and it seems to be working like I would expect.

public List<String> filterRiskLevel(String target, List<string> results)
{
      filterRiskLevel(target, root, results);
      return results;
}
private void search(String target, Node ptr, List<string> results)
{
     if (ptr != null)
     {
         if (ptr.riskLevel.Equals(target))
             results.Add("Audit ID: " + ptr.auditID +
                  "\n" + "Risk Level: " + ptr.riskLevel +
                  "\n" + "Scanner Found In: " + ptr.scanner +
                  "\n" + "Device Affected: " + ptr.boxName +
                  "\n" + "Description: " + ptr.description + "\n");
              filterRiskLevel(target, ptr.left, results);
              filterRiskLevel(target, ptr.right, results);
     }
}

Answer 2

I'm assuming that extra results are located in the 'right' subtree of previous results.
You had some problems with your code:

1. you can only return 1 result

2. you replace the ptr node with root in the beginning?!

   private void Search(String target, Node ptr, List<string> results)
   {
       if (ptr == null)
       {
           return;
       }
   
       int compare = target.CompareTo(ptr.riskLevel.ToString());
       if (compare == 0)
       {
           string result = "Audit ID: " + ptr.auditID  + 
               "\n" + "Risk Level: " + ptr.riskLevel + 
               "\n" + "Scanner Found In: " + ptr.scanner + 
               "\n" + "Device Affected: " + ptr.boxName + 
               "\n" + "Description: " + ptr.description + "\n";
           results.Add(result);
   
           search(target, ptr.right, results);
       }
       else if (compare < 0)
       {
           search(target, ptr.left, results);
       }
       else
       {
           search(target, ptr.right, results);
       }
   }
   
   public virtual List<string> search(String target)
   {
       var results = new List<string>();
       search(target, root, results);
       return results;
   }