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namespace aoc2019;
public sealed class Day15 : Day
{
private readonly bool verbose = false;
private readonly IntCodeVM vm;
public Day15() : base(15, "Oxygen System")
{
vm = new IntCodeVM(Input.First());
}
public override string Part1()
{
vm.Reset();
var currentLocation = new Location(0, 0);
var halt = IntCodeVM.HaltType.Waiting;
while (halt == IntCodeVM.HaltType.Waiting)
{
var direction = currentLocation!.NextDirection();
if (direction <= 4)
{
var (x, y) = currentLocation.Neighbor(direction);
if (Location.GetLocation(x, y) == null)
{
halt = vm.Run(direction);
currentLocation = vm.Result switch
{
Location.Wall => new Location(x, y, Location.Opposites[direction], Location.Wall),
Location.Empty => new Location(x, y, Location.Opposites[direction]),
Location.System => new Location(x, y, Location.Opposites[direction], Location.System),
_ => throw new Exception($"Unknown IntCodeVM response: {vm.Result}"),
};
}
}
else
{
direction = currentLocation.PreviousDirection;
if (direction > 0)
{
halt = vm.Run(direction);
currentLocation = vm.Result switch
{
Location.Empty or Location.System => Location.GetLocation(currentLocation.Neighbor(direction)),
_ => throw new Exception($"Unknown or unexpected response for previous room: {vm.Result}"),
};
}
else
{
if (verbose)
{
// find extents of canvas
int xMin, xMax, yMin, yMax;
xMin = yMin = int.MaxValue;
xMax = yMax = int.MinValue;
foreach (var (x, y) in Location.AllLocations.Keys)
{
if (x < xMin) xMin = x;
if (x > xMax) xMax = x;
if (y < yMin) yMin = y;
if (y > yMax) yMax = y;
}
Console.WriteLine($"Canvas extends from ({xMin}, {yMin}) to ({xMax}, {yMax})");
// print board
for (var y = yMin; y <= yMax; y++)
{
var line = "";
for (var x = xMin; x <= xMax; x++)
if (Location.AllLocations.ContainsKey((x, y)))
line += Location.AllLocations[(x, y)].Image();
else
line += "@";
Console.WriteLine(line);
}
}
currentLocation = Location.OxygenLocation;
var distance = 0;
while (currentLocation?.PreviousDirection != 0)
{
distance++;
currentLocation = Location.GetLocation(currentLocation!.PreviousLocation());
}
return $"{distance}";
}
}
}
return "";
}
public override string Part2()
{
var changed = true;
while (changed)
{
changed = false;
foreach (var location in Location.AllLocations.Values)
changed = location.UpdateDistanceToOxygenSystem() || changed;
}
return Location.AllLocations.Values
.Where(l => !l.IsWall)
.Max(l => l.DistanceToOxygenSystem)
.ToString();
}
private class Location
{
public const int Wall = 0;
public const int Empty = 1;
public const int System = 2;
private static readonly int[] Dx = { 0, 0, 0, 1, -1 };
private static readonly int[] Dy = { 0, 1, -1, 0, 0 };
public static readonly int[] Opposites = { 0, 2, 1, 4, 3 };
public static readonly Dictionary<(int x, int y), Location> AllLocations = new();
private readonly int currentType;
public int DistanceToOxygenSystem = int.MaxValue - 1;
private int searchDirection = 1;
public Location(int x, int y, int prev = 0, int type = Empty)
{
PreviousDirection = prev;
currentType = type;
X = x;
Y = y;
if (type == System)
{
OxygenLocation = this;
DistanceToOxygenSystem = 0;
// Console.WriteLine($"Found Oxygen System at ({x}, {y})");
}
AllLocations.Add((x, y), this);
}
public static Location? OxygenLocation { get; private set; }
public int PreviousDirection { get; }
private int X { get; }
private int Y { get; }
public bool IsWall => currentType == Wall;
public string Image()
{
return currentType switch
{
Wall => "\u2587",
Empty => X == 0 && Y == 0 ? "S" : " ",
System => "O",
_ => "?"
};
}
public bool UpdateDistanceToOxygenSystem()
{
if (currentType != Empty) return false;
foreach (var direction in Enumerable.Range(1, 4))
{
var distance = GetLocation(Neighbor(direction))?.DistanceToOxygenSystem ?? int.MaxValue;
if (distance + 1 < DistanceToOxygenSystem)
{
DistanceToOxygenSystem = distance + 1;
return true;
}
}
return false;
}
public (int, int) Neighbor(int direction)
{
return (X + Dx[direction], Y + Dy[direction]);
}
public (int, int) PreviousLocation()
{
return Neighbor(PreviousDirection);
}
public int NextDirection()
{
return searchDirection++;
}
public static Location? GetLocation(int x, int y)
{
return AllLocations.ContainsKey((x, y)) ? AllLocations[(x, y)] : null;
}
public static Location? GetLocation((int x, int y) coords)
{
return GetLocation(coords.x, coords.y);
}
}
}
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