/// <summary>
/// A* search pathfinding.
/// </summary>
/// <returns>Shortest path</returns>
public List <ButtonNode> FindPath()
{
// Reset the lists
openNodes.Clear();
closedNodes.Clear();
nextNodes.Clear();
// Add the start node as the first node to evaluate
openNodes.Add(new ButtonNode(gridManager.StartNode.Coordinates[0], gridManager.StartNode.Coordinates[1]));
// Create a goal node from the goal button
goalNode = new ButtonNode(gridManager.GoalNode.Coordinates[0], gridManager.GoalNode.Coordinates[1]);
// As long as there is a possible path
while (openNodes.Count != 0)
{
ButtonNode currentNode;
int newNodeIndex = 0;
if (openNodes.Count != 1)
{
// Get the index of the node with the lowest "f" distance
int minDistance = 100000;
for (int i = 0; i < openNodes.Count; i++)
{
currentNode = openNodes[i];
if (currentNode.CombinedDistance < minDistance)
{
minDistance = currentNode.DistanceToGoal;
newNodeIndex = i;
}
}
}
// Pop it from the list
currentNode = openNodes[newNodeIndex];
openNodes.RemoveAt(newNodeIndex);
// Get neighbour nodes
FindNextNodes(currentNode);
// Check if any are possible paths
for (int i = 0; i < nextNodes.Count; i++)
{
ButtonNode newNode = nextNodes[i];
// If the node is actually a goal node
if (newNode.Equals(goalNode))
{
// Get all the previous nodes from this path
List <ButtonNode> pathNodes = new List <ButtonNode>();
ButtonNode pathNode = currentNode;
while (pathNode.Parent != null)
{
pathNodes.Add(pathNode);
pathNode = pathNode.Parent;
}
return(pathNodes);
}
// Calculate the distances needed to determine if this node is any good
newNode.DistanceFromStart = currentNode.DistanceFromStart + 1;
newNode.DistanceToGoal = Mathf.Abs(newNode.X - goalNode.X) + Mathf.Abs(newNode.Y - goalNode.Y);
newNode.CombinedDistance = newNode.DistanceFromStart + newNode.DistanceToGoal;
// If there is a node with the same coordinates in the "frontier" list
// and it has a smaller combined distance skip this node
if (CheckOpenList(newNode))
{
continue;
}
// If there isn't a node with the same coordinates in the "closed" list
// with a smaller combined distance, then add it to the "frontier" list
if (!CheckClosedList(newNode))
{
openNodes.Add(newNode);
}
}
// Add the used node to the closed list
closedNodes.Add(currentNode);
}
return(null);
}
