// <summary>
// Walk the graph like it was a tree from the root - if you encounter a cycle, stop further walking
// and continue with the next node
// </summary>
// <param name="opeartion"></param>
// <param name="state"></param>
public void BreadthFirstSearchOperation(GraphNodeOperationDelegate operation, object state)
{
Queue <IGraphNode> pendingNodes = new Queue <IGraphNode>();
pendingNodes.Enqueue(this);
List <IGraphNode> visitedNodes = new List <IGraphNode>();
while (pendingNodes.Count != 0)
{
IGraphNode node = pendingNodes.Dequeue();
if (visitedNodes.Contains(node))
{
// cycle - already seen this node //
continue;
}
else
{
visitedNodes.Add(node);
}
operation(node, state);
foreach (IGraphNode child in node.Children)
{
pendingNodes.Enqueue(child);
}
}
}
public void DepthFirstSearchOperation(GraphNodeOperationDelegate preVisit, GraphNodeOperationDelegate postVisit, object state)
{
// nothing happens unless one operation is provided
if (preVisit == null && postVisit == null)
{
return;
}
// we must be able to distinguish these for the algorithm below to work
if (preVisit == postVisit)
{
throw new InvalidOperationException("Operations must be different.");
}
List <IGraphNode> visitedNodes = new List <IGraphNode>();
Stack <DepthFirstWalkInfo> frames = new Stack <DepthFirstWalkInfo>();
frames.Push(new DepthFirstWalkInfo {
CurrentNode = this, Operation = preVisit
});
while (frames.Count > 0)
{
DepthFirstWalkInfo current = frames.Pop();
if (visitedNodes.Contains(current.CurrentNode))
{
if (current.Operation == preVisit)
{
continue;
}
}
else
{
visitedNodes.Add(current.CurrentNode);
}
if (current.Operation != null)
{
current.Operation(current.CurrentNode, state);
}
if (current.Operation != postVisit)
{
frames.Push(new DepthFirstWalkInfo {
CurrentNode = current.CurrentNode, Operation = postVisit
});
// this goes into the stack in reverse order of what we need,
// put onto one stack then another to reverse it
Stack <DepthFirstWalkInfo> tempStack = new Stack <DepthFirstWalkInfo>();
foreach (IGraphNode child in current.CurrentNode.Children)
{
tempStack.Push(new DepthFirstWalkInfo {
CurrentNode = child, Operation = preVisit
});
}
while (tempStack.Count > 0)
{
frames.Push(tempStack.Pop());
}
}
}
}
public void DepthFirstSearchOperation(GraphNodeOperationDelegate operation, object state)
{
DepthFirstSearchOperation(operation, null, state);
}
