public SimplePathWithLenght(SimplePathWithLenght <NodeT> path, IArcWithLength <NodeT> arc)
: this(path.From, arc.To, new List <IArcWithLength <NodeT> >(path.Path) { arc }, path.Lenght + arc.Lenght)
{
if (path.To != arc.From)
{
throw new InvalidOperationException("To path node has to be the same as arcs From.");
}
}
public static ICollection <SimplePathWithLenght <NodeT> > FindShortestPaths <NodeT>(this ICollection <IArcWithLength <NodeT> > arcs, NodeT fromNode)
where NodeT : class
{
if (arcs == null)
{
throw new ArgumentNullException(nameof(arcs));
}
if (fromNode == null)
{
throw new ArgumentNullException(nameof(fromNode));
}
var shortestArcs = new Dictionary <NodeT, Dictionary <NodeT, IArcWithLength <NodeT> > >();
foreach (var arc in arcs)
{
if (arc.Lenght < 0)
{
throw new InvalidOperationException("Arcs with negative length are not allowed.");
}
Dictionary <NodeT, IArcWithLength <NodeT> > neighboors;
if (!shortestArcs.TryGetValue(arc.From, out neighboors))
{
shortestArcs[arc.From] = neighboors = new Dictionary <NodeT, IArcWithLength <NodeT> >();
}
IArcWithLength <NodeT> neighboor;
if (!neighboors.TryGetValue(arc.To, out neighboor) || arc.Lenght < neighboor.Lenght)
{
neighboors[arc.To] = arc;
}
}
var visitedNodes = new HashSet <NodeT>();
var currentPath = new SimplePathWithLenght <NodeT>(fromNode);
var foundPaths = new Dictionary <NodeT, SimplePathWithLenght <NodeT> > {
{ fromNode, currentPath }
};
while (currentPath != null)
{
var currentNode = currentPath.To;
SimplePathWithLenght <NodeT> nextPath = null;
Dictionary <NodeT, IArcWithLength <NodeT> > currentNeighboors;
if (shortestArcs.TryGetValue(currentNode, out currentNeighboors))
{
foreach (var arc in currentNeighboors.Values)
{
var newPath = new SimplePathWithLenght <NodeT>(currentPath, arc);
SimplePathWithLenght <NodeT> oldPath;
if (!foundPaths.TryGetValue(arc.To, out oldPath) || newPath.Lenght < oldPath.Lenght)
{
foundPaths[arc.To] = newPath;
}
if (nextPath == null || nextPath.Lenght > newPath.Lenght)
{
nextPath = newPath;
}
}
}
visitedNodes.Add(currentNode);
if (nextPath == null)
{
nextPath = foundPaths.Values.Where(p => !visitedNodes.Contains(p.To)).OrderBy(p => p.Lenght).FirstOrDefault();
}
currentPath = nextPath;
}
foundPaths.Remove(fromNode);
return(foundPaths.Values);
}
