private static void Relax(DijkstraNode v, DijkstraNode u)
{
int alt = u.Distance + PathfindingConstants.OrthogonalCost;
if (alt < v.Distance)
{
v.Distance = alt;
v.Parent = u;
}
}
private static DijkstraNode ExtractMin(ref List <DijkstraNode> Q)
{
int index = 0;
DijkstraNode min = Q[0];
for (int i = 1; i < Q.Count; ++i)
{
var curr = Q[i];
int comparison = curr.CompareTo(min);
if (comparison < 0)
{
min = curr;
index = i;
}
}
Q.RemoveAt(index);
return(min);
}
/// <summary>
/// Performs the Dijkstra searching algorithm to find the best paths to the goal node from any node.
/// </summary>
/// <param name="grid">The grid of nodes to solve (or search).</param>
/// <param name="goal">
/// The goal node. Note that there is no need for a starting node because this algorithm solves the
/// shortest path from any node to the goal node.
/// </param>
public static void SolveGrid(DijkstraNode[,] grid, DijkstraNode goal)
{
List <DijkstraNode> Q = new List <DijkstraNode>(grid.Length);
int cols = grid.GetLength(0);
int rows = grid.GetLength(1);
for (int c = 0; c < cols; ++c)
{
for (int r = 0; r < rows; ++r)
{
DijkstraNode v = grid[c, r];
if (!v.IsIllegal)
{
v.Reset();
Q.Add(v);
}
}
}
goal.Reset();
goal.Distance = 0;
while (Q.Count > 0)
{
// extra the minimum value
DijkstraNode u = ExtractMin(ref Q);
// relax each of the neighbors
foreach (DijkstraNode v in GetNeighbors(u.GetAdjacentPoints(), grid))
{
if (v == null || v.IsIllegal)
{
continue;
}
Relax(v, u);
}
}
}
