/// <summary>
/// backtracks from exit to start to identify the shortest route with the given Edges
/// returns invalid message if path is blocked or no edges
/// </summary>
/// <param name="predecessors"> list to backtrack</param>
/// <returns>Shortest route</returns>
public static string shortestPath(List <Edge> predecessors, MazeGrid maze)
{
int pCount = predecessors.Count - 1;
string shortestRoute = "";
Node prevNode;
if (maze.isNodeEqual(maze.exit, predecessors[pCount].To))
{
prevNode = predecessors[pCount].To;
}
else
{
Console.WriteLine("No possible routes, from B to A");
return("");
}
for (int i = predecessors.Count - 1; i >= 0; i--)
{
if (maze.isNodeEqual(predecessors[i].To, prevNode))
{
shortestRoute += predecessors[i].direction;
prevNode = predecessors[i].From;
}
}
char[] revert = shortestRoute.ToCharArray();
Array.Reverse(revert);
return(new string(revert));
}
/// <summary>
/// traverses the 2D array, in search of exit node and stops until it has reached the specified node or every node
/// </summary>
/// <returns></returns>
public static List <Edge> bfSearch(MazeGrid maze)
{
Queue <Node> queue = new Queue <Node>();
List <Edge> predecessors = new List <Edge>();
bool[,] visited = new bool[maze.h, maze.w];
for (int i = 0; i < maze.h; i++)
{
for (int j = 0; j < maze.w; j++)
{
visited[i, j] = false;
}
}
queue.Enqueue(maze.start);
visited[maze.start.I, maze.start.J] = true;
while (!(queue.Count == 0))
{
Node deQNode = queue.Dequeue();
Edge[] adjacentN = maze.adjacentNodes(deQNode);
foreach (Edge n in adjacentN)
{
if (n != null)
{
if (n.To != null)
{
if (!visited[n.To.I, n.To.J])
{
//end early if the exit has already been found
queue.Enqueue(n.To);
visited[n.To.I, n.To.J] = true;
predecessors.Add(n);
if (maze.isNodeEqual(n.To, maze.exit))
{
return(predecessors);
}
}
}
}
}
}
return(predecessors);
}