/// <summary>
/// Method: AStarTraversal
/// Input: Nil
/// Returns: list of locations
/// </summary>
public List<LocationInfo> AStarTraversal()
{
// Instantiate a priority queue
Queue queueOfNodes = new Queue();
// initial cost from start is made 0 and the heuristic cost to goal computed. parent node is also set to null
_startNode._costOfTraversal._g = 0.0;
_startNode._costOfTraversal._h = getEdgeDistance(_startNode, _endNode);
_startNode._parentNode = null;
// add the start node information to the open list and the priority queue
_openNodes.Add(_startNode);
queueOfNodes.enQueue(_startNode);
// variables for usage in the algorithm
LocationInfo visitingNode;
List<ConnectionInfo> neighborsList;
List<String> neighboringNodes;
String[] sNeighboringNodes;
LocationInfo openedNode;
while (queueOfNodes.queueLength > 0)
{ // when the priority queue is having some node
visitingNode = queueOfNodes.deQueue(); // remove the first item from the queue
_openNodes.Remove(visitingNode); // remove the corresponding node from the open list
if (visitingNode._node._node.Equals(_endNode._node._node))
{ // visiting node the same as the end node implies we are home
// track the parent nodes and insert them to the list of traversed locations to be printed
var finalTraversal = new List<LocationInfo> {
visitingNode
};
while (visitingNode._parentNode != null)
{
finalTraversal.Insert(0, visitingNode._parentNode);
visitingNode = visitingNode._parentNode;
}
return finalTraversal;
}
// use the linq feature in c# to find if the parent node and visiting node to get its neighbors list
var neighborsForVisitingNode = _connectionsInfo.Where(query => query._parentNode._node == visitingNode._node._node);
neighborsList = neighborsForVisitingNode.ToList(); // cast it to a list
neighboringNodes = new List<String>();
foreach (ConnectionInfo availableConnections in neighborsList)
neighboringNodes.Add(availableConnections._connectingNode._node); // add the node names to a string list
sNeighboringNodes = neighboringNodes.ToArray(); // cast it to a string array to be used later
// find the corresponding neighbor from the string array using linq feature and make a list of neighbors to visit
var neighborsVisitList = _locationsInfo.Where(query => sNeighboringNodes.Contains(query._node._node));
List<LocationInfo> neighbors = neighborsVisitList.ToList();
// iterate over each neighbor found
foreach (LocationInfo neighbor in neighbors)
{
if (_visitedNodes.Contains(neighbor))
continue;
// Update the traversal cost with the cost of the neighbor - g(n) from parent to neighbor
// and h(n) heuristic from neighbor to goal
double g_cost = visitingNode._costOfTraversal._g + getEdgeDistance(visitingNode, neighbor);
double h_cost = getEdgeDistance(neighbor, _endNode);
double newCostOfTraversal = g_cost + h_cost; // total cost f(n) = g(n) + h(n)
// use the linq feature in c# to find out the recently opened node from the open list
openedNode = _openNodes.FirstOrDefault(query => query._node._node == neighbor._node._node);
// make sure that the cost incurred due to traversing that neighbor is minimal
if (openedNode != null && openedNode._costOfTraversal.getCostOfTraversal() <= newCostOfTraversal)
continue;
// set the updated cost parameters of g(n) and h(n) in cost of traversal bean.
neighbor._costOfTraversal._g = g_cost;
neighbor._costOfTraversal._h = h_cost;
neighbor._parentNode = visitingNode; // make the visiting node the parent now and continue tracing the path.
if (openedNode != null)
{
_openNodes.Remove(neighbor); // remove the neighbor from the open list and queue
queueOfNodes.remove(openedNode);
}
_openNodes.Add(neighbor); // add the neighbor to the open list and queue
queueOfNodes.enQueue(neighbor);
}
_visitedNodes.Add(visitingNode); // add the current node the closed list
}
return null;
}
/// <summary>
/// Method: searchByLinks
/// Input: Nil
/// Returns: string of locations
/// </summary>
public string searchByLinks()
{
// Instantiate a priority queue
var queueOfNodes = new Queue<LocationInfo>();
_startNode._parentNode = null;
queueOfNodes.Enqueue(_startNode); //Adopt a BFS approach and add the start node to the queue
// variables for usage in the algorithm
LocationInfo visitingNode;
List<ConnectionInfo> neighborsList;
List<String> neighboringNodes;
String[] sNeighboringNodes;
LocationInfo openedNode;
while (queueOfNodes.Count > 0)
{
visitingNode = queueOfNodes.Dequeue(); //Dequeue the first element
if (visitingNode._node._node.Equals(_endNode._node._node))
{
var finalTraversal = new List<LocationInfo> { visitingNode };
while (visitingNode._parentNode != null)
{
finalTraversal.Insert(0, visitingNode._parentNode);
visitingNode = visitingNode._parentNode;
}
foreach (LocationInfo minLinkNode in finalTraversal)
_minLinkPath += minLinkNode._node._node + ',';
_minLinkPath.TrimEnd(',');
return _minLinkPath;
}
// use the linq feature in c# to find if the parent node and visiting node to get its neighbors list
var neighborsForVisitingNode = _connectionsInfo.Where(query => query._parentNode._node == visitingNode._node._node);
neighborsList = neighborsForVisitingNode.ToList(); // cast it to a list
neighboringNodes = new List<String>();
foreach (ConnectionInfo availableConnections in neighborsList)
neighboringNodes.Add(availableConnections._connectingNode._node); // add the node names to a string list
sNeighboringNodes = neighboringNodes.ToArray(); // cast it to a string array to be used later
// find the corresponding neighbor from the string array using linq feature and make a list of neighbors to visit
var neighborsVisitList = _locationsInfo.Where(query => sNeighboringNodes.Contains(query._node._node));
List<LocationInfo> neighbors = neighborsVisitList.ToList();
// iterate over each neighbor found
foreach (LocationInfo neighbor in neighbors) {
if (_visitedNodes.Contains(neighbor))
continue;
// use the linq feature in c# to find out the recently opened node from the open list
openedNode = _openNodes.FirstOrDefault(query => query._node._node == neighbor._node._node);
if (openedNode == null && !queueOfNodes.Contains(neighbor)) {
neighbor._parentNode = visitingNode;
queueOfNodes.Enqueue(neighbor);
}
}
_visitedNodes.Add(visitingNode);
}
return null;
}