/// <summary>
/// Determines whether the current path traverses the same
/// nodes as the specified path in the same order, disregard
/// which one is the starting node.
/// </summary>
public bool SameCycle(Path path)
{
ArrayList items = path._items.Clone() as ArrayList;
if (items.Count != _items.Count)
return false;
int iterations = items.Count;
for (int i = 0; i < iterations; i++)
{
if (SameCycle(items))
return true;
object item = items[0];
items.RemoveAt(0);
items.Add(item);
}
return false;
}
/// <summary>
/// Finds the longest path in the graph. The time limit
/// specifies the maximum duration of the search process
/// in milliseconds.
/// Returns null if no path exists.
/// </summary>
public static Path FindLongestPath(IGraph graph, long timeLimit)
{
PathList paths = new PathList();
// create initial set of paths of length zero
foreach (INode node in graph.Nodes)
{
// create a path consisting only of this node
Path path = new Path();
path.Add(node);
paths.Add(path);
// paths in which this node participates
PathStats pathStats = new PathStats();
pathStats.currentSet.Add(path, path);
node.Data = pathStats;
}
long startMillis = DateTime.Now.Ticks / 10000;
// find set of paths that are one node longer than in previous set
bool morePathsAdded = false;
do
{
morePathsAdded = false;
PathList newPaths = new PathList();
// try to extend each path in the previous set
foreach (Path path in paths)
{
INode lastNode = path.Nodes[path.Nodes.Count - 1];
foreach (ILink link in lastNode.OutLinks)
{
INode nodeToAdd = graph.Directed ?
link.Destination : link.GetOppositeNode(lastNode);
// test for cycles
PathStats testPaths = nodeToAdd.Data as PathStats;
if (testPaths.currentSet.Contains(path)) continue;
// extend the path with this node
Path newPath = new Path(path);
newPath.Add(link, nodeToAdd);
// update all nodes in the new path
foreach (INode node in newPath.Nodes)
{
PathStats nodePaths = node.Data as PathStats;
nodePaths.newSet.Add(newPath, newPath);
}
// add to the new set
morePathsAdded = true;
newPaths.Add(newPath);
}
}
if (morePathsAdded)
{
paths = newPaths;
// remove shorter paths from node associated path lists
// they are not needed in next iterations
foreach (INode node in graph.Nodes)
{
PathStats nodePaths = node.Data as PathStats;
Hashtable swap = nodePaths.currentSet;
nodePaths.currentSet = nodePaths.newSet;
nodePaths.newSet = swap;
nodePaths.newSet.Clear();
}
}
// Check time limit
if (timeLimit > 0 &&
DateTime.Now.Ticks / 10000 - startMillis > timeLimit)
break;
}
while (morePathsAdded);
// cleanup
foreach (INode node in graph.Nodes)
node.Data = null;
if (paths.Count == 0) return null;
return paths[0];
}
private static PathList FindPaths(IGraph graph,
INode from, INode to, bool shortestOnly)
{
PathList result = new PathList();
Path path = null;
if (from == to && shortestOnly)
{
// Return a collection with a single path consisting of a single node.
path = new Path();
path.Add(from);
result.Add(path);
return result;
}
// Perform the search
PathList tempCol = new PathList();
Path tempPath;
// Create the first path, constisting only of the first node
tempCol.Add(tempPath = new Path());
tempPath.Add(from);
bool pathFound = false;
while (true)
{
int size = tempCol.Count;
if (size == 0)
break;
if (pathFound && shortestOnly)
break;
// For all paths - get their next nodes
for (int i = 0; i < size; i++)
{
tempPath = tempCol[0];
tempCol.RemoveAt(0);
// Get the last node for this path and find its successors
INode lastNode = tempPath.Nodes[tempPath.Nodes.Count - 1];
LinkCollection links = lastNode.OutLinks;
foreach (ILink link in links)
{
INode nextNode;
// Get the next node in the path
nextNode = graph.Directed ?
link.Destination : link.GetOppositeNode(lastNode);
// Check if the path target is reached
if (nextNode.Equals(to))
{
// We've reached the end
Path newPath = new Path(tempPath);
newPath.Add(link, nextNode);
result.Add(newPath);
pathFound = true;
continue;
}
// The node does not belong to the path -> add it
if (!tempPath.Contains(nextNode))
{
Path newPath = new Path(tempPath);
newPath.Add(link, nextNode);
tempCol.Add(newPath);
}
}
}
}
return result;
}
public Path(Path p)
{
_nodes = p._nodes.Clone() as NodeCollection;
_links = p._links.Clone() as LinkCollection;
_items = p._items.Clone() as ArrayList;
}
public bool Contains(Path p)
{
return List.Contains(p);
}
public void Remove(Path p)
{
List.Remove(p);
}
public void Insert(int i, Path p)
{
List.Insert(i, p);
}
public void Add(Path p)
{
List.Add(p);
}
