public IEnumerable <Day17MazeState> GetNextStates(Day17MazeState state)
{
if (state.Location.X == 3 && state.Location.Y == 3)
{
yield break;
}
//Console.WriteLine(state.Path);
var hash = _hasher.Md5Hash(state.Path).ToLower();
if (IsOpen(hash[0]) && state.Location.Y > 0) //Up
{
yield return(new Day17MazeState(state, CompassBearing.North));
}
if (IsOpen(hash[1]) && state.Location.Y < 3) //Down
{
yield return(new Day17MazeState(state, CompassBearing.South));
}
if (IsOpen(hash[2]) && state.Location.X > 0) //Left
{
yield return(new Day17MazeState(state, CompassBearing.West));
}
if (IsOpen(hash[3]) && state.Location.X < 3) //Left
{
yield return(new Day17MazeState(state, CompassBearing.East));
}
}
public string Solve(string passcode)
{
var startState = new Day17MazeState {
Location = new Location(0, 0), Path = passcode
};
HashSet <Day17MazeState> toExplore = new HashSet <Day17MazeState> {
startState
};
List <string> validRoutes = new List <string>();
while (toExplore.Any())
{
toExplore = new HashSet <Day17MazeState>(toExplore.SelectMany(GetNextStates));
var success = toExplore.Where(x => x.Location.X == 3 && x.Location.Y == 3);
if (success.Any())
{
return(success.OrderBy(x => x.Path.Length).First().Path.Remove(0, passcode.Length));
}
}
return(validRoutes.OrderBy(x => x.Length).First().Remove(0, passcode.Length));
}
public Day17MazeState(Day17MazeState state, CompassBearing direction)
{
Path = state.Path;
Location = new Location(state.Location.X, state.Location.Y);
Path = state.Path + GetNextPath(direction);
if (direction == CompassBearing.North)
{
Location.Y--;
}
else if (direction == CompassBearing.East)
{
Location.X++;
}
else if (direction == CompassBearing.South)
{
Location.Y++;
}
else if (direction == CompassBearing.West)
{
Location.X--;
}
}
protected bool Equals(Day17MazeState other)
{
return(string.Equals(Path, other.Path) && Equals(Location, other.Location));
}