public override async ValueTask <string> Solve_1()
{
var dest = _grid.BottomRight;
var s = new AStarSearch <Point>(null, Expand);
var path = s.FindFirst(new Point(0, 0), x => x == dest, x => x.ManhattanDistTo(dest)) !;
var totalRisk = path.Cost;
return(totalRisk.ToString());
IEnumerable <(Point node, float cost)> Expand(Point p)
{
foreach (var n in _grid.Get4NeighborsOf(p))
{
yield return(n, _grid[n] - '0');
private static char Step(FiniteGrid2D <char> map, Point p)
{
var neighborCount = map.Get4NeighborsOf(p).Count(n => map[n] == '#');
return(StepChar(map[p], neighborCount));
}