public string Solve(string input)
{
string[] inputLines = input.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
int yOffset = inputLines[0].Length;
string map = string.Concat(inputLines);
// Find the minecarts
List <Minecart> minecarts = Minecart.FindInMap(ref map, yOffset);
while (true)
{
// First, sort the minecarts by their position...
minecarts = minecarts.OrderBy(x => x.Position).ToList();
// Now move them all...
foreach (Minecart current in minecarts)
{
current.Position += current.NextMove;
current.SetNextMove(yOffset, map[current.Position]);
// Has it crashed?
if (current.GetCrashedIntoMinecart(minecarts) != null)
{
return($"{current.Position % yOffset},{current.Position / yOffset}");
}
}
}
}
public string Solve(string input)
{
string[] inputLines = input.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
int yOffset = inputLines[0].Length;
string map = string.Concat(inputLines);
// Find the minecarts
List <Minecart> minecarts = Minecart.FindInMap(ref map, yOffset);
// We won't be able to just remove carts from the collection as we go,
// so we keep a list of those that have been removed
var removedCarts = new List <Minecart>();
while (true)
{
// First, sort the minecarts by their position...
minecarts = minecarts.OrderBy(x => x.Position).ToList();
// Now move the ones that haven't crashed...
foreach (Minecart current in minecarts)
{
if (removedCarts.Contains(current))
{
continue;
}
current.Position += current.NextMove;
current.SetNextMove(yOffset, map[current.Position]);
// Has it crashed?
Minecart crashedIntoMinecart = current.GetCrashedIntoMinecart(minecarts.Where(x => !removedCarts.Contains(x)));
if (crashedIntoMinecart != null)
{
removedCarts.Add(current);
removedCarts.Add(crashedIntoMinecart);
}
}
// At the end of the tick - is there only one remaining?
if (minecarts.Count - removedCarts.Count == 1)
{
Minecart lastCart = minecarts.First(x => !removedCarts.Contains(x));
return($"{lastCart.Position % yOffset},{lastCart.Position / yOffset}");
}
}
}
public static void TurnLeft(this Minecart cart, int yOffset)
{
if (cart.NextMove == -1)
{
cart.NextMove = yOffset;
}
else if (cart.NextMove == 1)
{
cart.NextMove = -yOffset;
}
else if (cart.NextMove == yOffset)
{
cart.NextMove = 1;
}
else
{
cart.NextMove = -1;
}
}
public static void SetNextMove(this Minecart cart, int yOffset, char currentRail)
{
// Now work out where it'll go next
// We only care if it's on something that'll change it's direction...
if (currentRail == '/' && (cart.NextMove == -1 || cart.NextMove == 1))
{
// Coming to a left turn
cart.TurnLeft(yOffset);
}
else if (currentRail == '/')
{
// Coming to a right turn
cart.TurnRight(yOffset);
}
else if (currentRail == '\\' && (cart.NextMove == -1 || cart.NextMove == 1))
{
// Coming to a right turn from the left
cart.TurnRight(yOffset);
}
else if (currentRail == '\\')
{
// Coming to a left turn from the bottom
cart.TurnLeft(yOffset);
}
else if (currentRail == '+')
{
switch (cart.NextIntersectionBehavior % 3)
{
case 0:
cart.TurnLeft(yOffset);
break;
case 2:
cart.TurnRight(yOffset);
break;
}
cart.NextIntersectionBehavior++;
}
}
public static Minecart GetCrashedIntoMinecart(this Minecart cart, IEnumerable <Minecart> otherMinecarts)
{
return(otherMinecarts.FirstOrDefault(x => x != cart && x.Position == cart.Position));
}
public static void TurnRight(this Minecart cart, int yOffset)
{
cart.TurnLeft(yOffset);
cart.NextMove *= -1;
}
