AdventOfCode/AdventOfCode.Core/Shared/A-Star/AStarGrid.cs

namespace AdventOfCode.Core.Shared.A_Star
{
    public class AStarGrid : Grid<AStarNode>
    {
        const int TILE_MOVE_COST = 10;

        public AStarGrid(AStarNode[] data) : base(data)
        {
        }

        public int MinimalSteps(AStarNode start, AStarNode destination)
        {
            List<AStarNode> closedNodes = new();
            List<AStarNode> openNodes = new List<AStarNode> { start };

            do
            {
                AStarNode current = openNodes.OrderBy(n => n.FCost).First();
                openNodes.Remove(current);
                current.CloseNode();
                closedNodes.Add(current);

                if (current == destination)
                {
                    //done
                    return 1;
                }

                var neighbors = GetNeighbors(current, false);
                neighbors = neighbors.Where(n => current.CanMoveTo(n));

                // calc costs
                foreach(AStarNode neighbor in neighbors)
                {
                    neighbor.ParentNode = current;
                    // since we only move straight the move cost is always the same
                    neighbor.GCost = current.GCost + TILE_MOVE_COST;
                    neighbor.HCost = neighbor.DistanceTo(destination) * TILE_MOVE_COST;
                    neighbor.OpenNode();
                    openNodes.Add(neighbor);
                }
            }
            while (true);
        }
    }
}