public static DijkstraPath GetDijkstraPath(DirectionalGraph graph, int startId, int destinationId)
{
var nodes = graph.Nodes;
var start = NodeUtil.GetNodeWithId(nodes, startId);
var destination = NodeUtil.GetNodeWithId(nodes, destinationId);
if (start == null || destination == null)
{
return(null);
}
var accumulativeDistance = 0;
var cur = start;
cur.LowestDistance = 0;
do
{
//3. For ea connected
cur.Edges.ForEach(edge =>
{
// set distanceFromCurrent = accumulative length + length to node
var distanceFromCurrent = accumulativeDistance + edge.Value;
//4. If node has no distance marked, or distanceFromCurrent<marked node distance...
var connectedNode = NodeUtil.GetNodeWithId(nodes, edge.NodeId);
if (!connectedNode.LowestDistance.HasValue || distanceFromCurrent < connectedNode.LowestDistance.Value)
{
// set marked node distance to distanceFromCurrent
connectedNode.LowestDistance = distanceFromCurrent;
}
});
//4. Once all nodes marked, mark current node as visited
cur.Visited = true;
//5. Stop if at destination node
if (cur == destination)
{
break;
}
//6. Else goto the unvisited node with lowest value
cur = GetPrevNodeForPath(nodes);
//7. Set accumulativeDistance = node value
if (!cur.LowestDistance.HasValue)
{
throw new ArgumentNullException("Tried to get lowestDistance value for a Node, but there was none");
}
accumulativeDistance = cur.LowestDistance.Value;
//8. repeat from 3.
} while (cur != null);
// Get path
return(new DijkstraPath(nodes, start, destination));
// then make it multi-threaded
}
static Node GetPrevWithLowestValue(List <Node> nodes, Node fromNode)
{
// For ea prev
Node nodeWithLowestValue = null;
var edges = fromNode.Edges;
for (int e = 0; e < edges.Count; e++)
{
var connectedNodeId = edges[e].NodeId;
var connectedNode = NodeUtil.GetNodeWithId(nodes, connectedNodeId);
var prevNodeValue = connectedNode.LowestDistance;
if (nodeWithLowestValue == null || (prevNodeValue.HasValue && prevNodeValue.Value < nodeWithLowestValue.LowestDistance))
{
nodeWithLowestValue = connectedNode;
}
}
// Return one with lowest val
return(nodeWithLowestValue);
}