Returning multiple nodes when searching a tree/trie?

Question

I have constructed a suffix trie, a tree containing all the suffixes of a string, where each node contains only one character, with a SuffixNode at the end of each path which contains the locations of the suffixes within the string.

Let's say my trie contains the words, "Cat", "Car" and "Can" and I want to search for "Ca", the result should return 3 suffix nodes since the search string is found in 3 different places. I managed to search the tree for "Ca", but once I reach that point, I don't know how to continue traversing the children of the 'a' node to find all the suffix nodes.

I was thinking of using some sort of collection to add the suffix nodes to and then return the collection. Does this approach make sense, or are there better solutions?

I have solved the searching problem below. The reason it wasn't returning any nodes has to do with the creation of the tree and the differences between nodes:

public void SearchTrie(Node parent, String s, List<SuffixNode> suffixes)
    {
        Node n = FindNode(parent, s);
        FindSuffixes(n, suffixes);
    }

    private void FindSuffixes(Node parent,List<SuffixNode> suffixes)
    {            
        if (parent is SuffixNode)
        {
            suffixes.Add((SuffixNode)parent);
        }
        else
        {
            foreach (KeyValuePair<char, Node> child in parent.children)
            {
                FindSuffixes(child.Value, suffixes);
            }
        }
    }

    private Node FindNode(Node parent, String s)
    {
        if ((s.Length == 1) && parent.children.ContainsKey(s[0]))
        {
            Node n = parent.children[s[0]];
            return n;
        }

        while (s[0].ToString() != "")
        {
            if (parent.children.ContainsKey(s[0]))
            {
                if ((s.Length > 1))
                {
                    return FindNode(parent.children[s[0]], s.Substring(1));
                }

            }
            else
            {
                break;
            }

        }

        return null;
    }

Node:

class Node
{
    public char label;
    public Node parent;
    public Dictionary<char,Node> children;

    public Node(Node NewParent, char NewLabel)
    {
        this.parent = NewParent;
        this.label = NewLabel;
        children=new Dictionary<char,Node>();
    }
}

Could you please post some code/examples ? It could help to understand the question... because IMO you should simply traverse the subtree (below "CA")... — digEmAll, Mar 17 '12 at 11:40
That's what I'm trying to do, but I'm finding it a bit difficult. I'll post my previous search function, which other code would be useful? — Matt, Mar 17 '12 at 11:50
I updated my question with my new search method and the node class — Matt, Mar 17 '12 at 12:34

H H · Accepted Answer · 2012-03-17T13:28:28.320

3

I was thinking of using some sort of collection to add the suffix nodes to and then return the collection.

That would be the first choice.

..., or are there better solutions?

There are other solutions, like

filling a list supplied by the caller
use an iterator block with yield return

But w/o any special requirements, fill a List<string> and return it as IEnumerable<string>.

edited Mar 17 '12 at 13:28

answered Mar 17 '12 at 12:28

H H

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Returning multiple nodes when searching a tree/trie?

1 Answers1