Question

I need to find a path or paths down a complicated graph structure. The graph is built using something similar to this:

class Node {     public string Value { get; set;}     public List<Node> Nodes { get; set;}      public Node()     {         Nodes = new List<Node>();     } } 

What makes this complicated is that the nodes can reference back to an earlier node. For example,

A -> C -> E -> A

What I need to do is get a list of stacks which represent paths through the Nodes until I get to a Node with a specific value. Since its possible there can be some very large paths available we can have a maximum Nodes to try.

List<Stack<Node>> paths = FindPaths(string ValueToFind, int MaxNumberNodes); 

Does anyone have a way to build this (or something similar)? I’ve done recursion in the past but I’m having a total brain fart thinking about this for some reason. My question specified a lambda expression but using a lambda is not necessarily required. I’d be grateful for any solution.

Side note: I lifted the class from aku’s excellent answer for this recursion question. While his elegant solution shown below traverses the tree structure it doesn’t seem to allow enough flexibility to do what I need (for example, dismiss paths that are circular and track paths that are successful).

Action<Node> traverse = null; traverse = (n) => { Console.WriteLine(n.Value); n.Nodes.ForEach(traverse);}; traverse(root);  // where root is the tree structure 

Edit:

Based on input from the comments and answers below I found an excellent solution over in CodeProject. It uses the A* path finding algorithm. Here is the link.

Answer 1

If you’re issue is related to Pathfinding, you may want to google for ‘A star’ or ‘A*’. Its a common and efficient pathfinding algorithm. See this article for an example directly related to your problem.

You may also want to look at the Dijsktra Algorithm