public void FindPath(MapPosition startPosition, MapPosition endPosition, ref List <MapPosition> results)
{
if (results == null)
{
results = new List <MapPosition>();
}
results.Clear();
// if(the locations are the same then ... exit this procedure.
if (object.Equals(startPosition, endPosition))
{
return;
}
// Add the starting square to the open list.
NodesCollection openedNodes = new NodesCollection();
NodesCollection closedNodes = new NodesCollection();
openedNodes.Add(startPosition);
MapCellsCollection parentNodes = new MapCellsCollection();
int lowestItem, foundItem, nodeIndex, parentIndex;
NodeItem currentNode;
List <MapPosition> connectingNodes = new List <MapPosition>();
do
{
// ... Look for the lowest F cost square on the open list ...
lowestItem = openedNodes.FindByLowestF();
if (lowestItem < 0)
{
return;
}
currentNode = openedNodes[lowestItem];
// ... Switch it to the close list ...
closedNodes.Add(currentNode);
openedNodes.RemoveAt(lowestItem);
// ... if(we added the target square to the closed list, then quit.
if (object.Equals(currentNode.Position, endPosition))
{
break;
}
// ... for(each of the cell's sides to this current square ...
this.EnumConnectingNodes(currentNode.Position, ref connectingNodes);
if (connectingNodes != null && connectingNodes.Count > 0)
{
for (nodeIndex = 0; nodeIndex < connectingNodes.Count; nodeIndex++)
{
if (closedNodes.FindIndex(connectingNodes[nodeIndex]) < 0)
{
// ... Find if the cell is in the open list ...
foundItem = openedNodes.FindIndex(connectingNodes[nodeIndex]);
// ... if(the cell isn't in the open list then add it ...
if (foundItem < 0)
{
openedNodes.Add(connectingNodes[nodeIndex], (currentNode.G + 1), connectingNodes[nodeIndex].GetDistance(endPosition));
parentIndex = parentNodes.FindIndex(connectingNodes[nodeIndex]);
if (parentIndex < 0)
{
parentNodes.Add(connectingNodes[nodeIndex], currentNode.Position);
}
else
{
parentNodes[parentIndex].Next = currentNode.Position;
}
}
else
{
if (openedNodes[foundItem].G < currentNode.G)
{
openedNodes[foundItem].G = (currentNode.G + 1);
parentIndex = parentNodes.FindIndex(connectingNodes[nodeIndex]);
if (parentIndex < 0)
{
parentNodes.Add(connectingNodes[nodeIndex], currentNode.Position);
}
else
{
parentNodes[parentIndex].Next = currentNode.Position;
}
}
}
}
} //nodeIndex
}
} while(true);
// Add the last cell to the list.
results.Insert(0, (MapPosition)endPosition.Clone());
// Now that we're done, let's check the results and return it.
int currentAddress = parentNodes.FindIndex(endPosition);
do
{
if (currentAddress < 0 || (parentNodes[currentAddress].Next == null || parentNodes[currentAddress].Next.IsEmpty()))
{
break;
}
else
{
if (!object.Equals(parentNodes[currentAddress].Next, startPosition))
{
results.Insert(0, (MapPosition)parentNodes[currentAddress].Next.Clone());
}
currentAddress = parentNodes.FindIndex(parentNodes[currentAddress].Next);
}
} while(true);
} // FindPath
