public override bool Equals(object obj)
{
if (this == obj)
{
return(true);
}
Day20GridState that = (Day20GridState)obj;
return(this.Point.Equals(that.Point) &&
this.Level == that.Level);
}
private void Visit(
Queue <Day20GridState> q,
HashSet <Day20GridState> visited,
Day20GridState state,
int xDelta,
int yDelta)
{
Day20GridState newState = null;
int newX = state.Point.X + xDelta;
int newY = state.Point.Y + yDelta;
var p = new Point(newX, newY);
if (!grid.ContainsKey(p))
{
// not in the grid, can't move here
newState = null;
}
else
{
char c = grid[p];
if (c == '.')
{
// movable space
newState = new Day20GridState
{
FromState = state,
Steps = state.Steps + 1,
Point = new Point(newX, newY),
Level = state.Level
};
}
else
{
// hit a wall
newState = null;
}
}
if (newState != null)
{
if (visited.Add(newState))
{
q.Enqueue(newState);
}
}
}
private int GetDistanceBfs(Day20GridState start, bool useLevels)
{
Queue <Day20GridState> q = new Queue <Day20GridState>();
HashSet <Day20GridState> visited = new HashSet <Day20GridState>();
q.Enqueue(start);
visited.Add(start);
while (q.Any())
{
Day20GridState state = q.Dequeue();
var thisPortal = portals.FirstOrDefault(p => p.OutputLocation.Equals(state.Point));
string portalName = (thisPortal == null ? null : thisPortal.Name);
// we have reached a portal
if (portalName != null)
{
if (state.Level == 0 && portalName == "ZZ")
{
// this is the exit to the maze
return(state.Steps);
}
// get portals with this name -- there will be two
// unless it's AA. If it's one of the others, we
// need to queue up a location that is the other
// portal
var allPortals = portals.Where(p => p.Name.Equals(portalName));
foreach (var p in allPortals)
{
// if it's not the one we're already on
if (!p.OutputLocation.Equals(state.Point))
{
int newLevel = 0;
if (useLevels)
{
newLevel = state.Level + CalculateLevel(state.Point);
}
if (!useLevels || (useLevels && newLevel >= 0))
{
// teleport!
Day20GridState newState = new Day20GridState
{
Point = p.OutputLocation,
Steps = state.Steps + 1,
FromState = state,
Level = newLevel
};
if (visited.Add(newState))
{
q.Enqueue(newState);
}
}
}
}
}
Visit(q, visited, state, -1, 0);
Visit(q, visited, state, 1, 0);
Visit(q, visited, state, 0, -1);
Visit(q, visited, state, 0, 1);
}
throw new InvalidOperationException();
}