/// <summary>
/// Adds a node to the graph
/// </summary>
/// <param name="node">The node to be added</param>
public void AddNavNode(NavNode node)
{
Nodes.Add(node);
//set the bounds of the grid
if (node.Indexes.Item1 > maxX)
{
maxX = node.Indexes.Item1;
}
if (node.Indexes.Item2 > maxY)
{
maxY = node.Indexes.Item2;
}
}
/// <summary>
/// Uses a modification of Dijkstra Shortest Path Algorithm to find
/// the farthest path away from the target node, relative to the
/// "from" node
/// </summary>
/// <param name="from">The starting node</param>
/// <param name="target">The target node to run way from</param>
/// /// <param name="exclude">Nodes of the types in the list won't be considered</param>
/// <returns>A list containing the shortest path between the given nodes</returns>
public List <NavNode> FarthestPath(NavNode from, NavNode target, List <NodeType> exclude = null)
{
List <NavNode> result = new List <NavNode>();
//limits the path size for performance
const int maxSize = 10;
int greatestDistance = 0;
//mark all nodes as unvisited
//set the distance to "- infinity"
//and clear the path
foreach (var node in Nodes)
{
node.Visited = false;
node.Distance = int.MinValue;
node.PreviousNodeInPath = null;
}
//set the from node distance to 0
from.Distance = 0;
//the current node, set it to "from"
NavNode currentNode = from;
//number of nodes yet to be visited - target
int nodesToBeVisited = Nodes.Count - 1;
//iterate trhough the nodes until the
//"to" node is visited
while (nodesToBeVisited > 0 || greatestDistance < maxSize)
{
//mark current node as visited
//and remove a node to be visited
currentNode.Visited = true;
nodesToBeVisited--;
//calc the distance to the neighbors
foreach (var neighbor in currentNode.Neighbors)
{
//if the neighbor is already visited, ignore it
if (neighbor == null || neighbor.Visited)
{
continue;
}
//ignore target
if (neighbor == target)
{
continue;
}
//ignore neighbor if it matches any exluded type
if (exclude != null && exclude.Contains(neighbor.NodeType))
{
continue;
}
//cumulative distance from the starting node
int distance = currentNode.Distance + 1;
if (distance > neighbor.Distance)
{
neighbor.Distance = distance;
neighbor.PreviousNodeInPath = currentNode;
if (distance > greatestDistance)
{
greatestDistance = distance;
}
}
}
//change the current node to the non-visited
//node with the greatest distance
currentNode = Nodes.Where(n => !n.Visited && n != target).OrderByDescending(n => n.Distance).FirstOrDefault();
}
//fill the result starting from the node with greatest distance
currentNode = Nodes.Where(n => n != target).OrderByDescending(n => n.Distance).FirstOrDefault();
while (greatestDistance > 0)
{
greatestDistance--;
result.Add(currentNode.PreviousNodeInPath);
currentNode = currentNode.PreviousNodeInPath;
}
result.Reverse();
return(result.ToList());
}
/// <summary>
/// Uses Dijkstra Shortest Path Algorithm to find the shortest path
/// between the given nodes, using adjacency matrix representation
/// and fixing the distance between neighbor nodes as 1
/// </summary>
/// <param name="from">The starting node</param>
/// <param name="to">The target node</param>
/// /// <param name="exclude">Nodes of the types in the list won't be considered</param>
/// <returns>A list containing the shortest path between the given nodes</returns>
public List <NavNode> ShortestPath(NavNode from, NavNode to, List <NodeType> exclude = null)
{
List <NavNode> result = new List <NavNode>();
//mark all nodes as unvisited
//set the distance to "infinity"
//and clear the path
foreach (var node in Nodes)
{
node.Visited = false;
node.Distance = int.MaxValue;
node.PreviousNodeInPath = null;
}
//set the from node distance to 0
from.Distance = 0;
//the current node, set it to "from"
NavNode currentNode = from;
//iterate trhough the nodes until the
//"to" node is visited
while (!to.Visited)
{
//mark current node as visited
//and remove a node to be visited
currentNode.Visited = true;
//calc the distance to the neighbors
foreach (var neighbor in currentNode.Neighbors)
{
//if the neighbor is already visited, ignore it
if (neighbor == null || neighbor.Visited)
{
continue;
}
//ignore neighbor if it matches any exluded type
if (exclude != null && exclude.Contains(neighbor.NodeType))
{
continue;
}
//cumulative distance from the starting node
int distance = currentNode.Distance + 1;
if (distance < neighbor.Distance)
{
neighbor.Distance = distance;
neighbor.PreviousNodeInPath = currentNode;
}
}
//change the current node to the non-visited
//node with the shortest distance
currentNode = Nodes.Where(n => !n.Visited).OrderBy(n => n.Distance).FirstOrDefault();
}
//fill the result
result.Add(to);
currentNode = to;
while (currentNode != from)
{
result.Add(currentNode.PreviousNodeInPath);
currentNode = currentNode.PreviousNodeInPath;
}
result.Reverse();
return(result.ToList());
}
