public Challenge()
{
_map = new CharMap(inputList.ToArray());
Dictionary <string, (Point a, Point b)> portals = new Dictionary <string, (Point, Point)>();
void CheckPortal(char c, Point pos, Point dir)
{
char c2 = _map.GetCharOrDefault(pos + dir);
if (!IsPortalID(c2))
{
return;
}
Point portal = _map.GetCharOrDefault(pos - dir) == '.' ? pos - dir : pos + dir * 2;
string id = $"{c}{c2}";
switch (id)
{
case "AA":
_map[portal] = 's';
_start = portal;
break;
case "ZZ":
_map[portal] = 'e';
_end = portal;
break;
default:
_map[portal] = IsOuterPortal(portal) ? '@' : '$';
if (!portals.ContainsKey(id))
{
portals[id] = (portal, Point.zero);
}
else
{
portals[id] = (portals[id].a, portal);
}
break;
}
}
foreach ((int x, int y, char c) in _map)
{
if (IsPortalID(c))
{
CheckPortal(c, new Point(x, y), Direction.Right);
CheckPortal(c, new Point(x, y), Direction.Down);
}
}
foreach ((Point a, Point b) in portals.Values)
{
_portalMap.Add(a, b);
}
}
private int FindShortestPath()
{
int GetH(Point p, Point end) => 0; // No heuristic (Dijsktra's/BFS)
bool IsValid(Point p) => ".se@$".Contains(_map.GetCharOrDefault(p));
HashSet <Point> GetNeighbors(Point p)
{
HashSet <Point> neighbors = new HashSet <Point>
{
p + new Point(1, 0), p + new Point(0, 1),
p + new Point(-1, 0), p + new Point(0, -1)
};
if ("@$".Contains(_map[p]))
{
neighbors.Add(_portalMap[p]);
}
return(neighbors);
}
return(Pathfinder.FindPath(_start, _end, IsValid, GetH, GetNeighbors).Count);
}