class Rail
{
public int X,Y;
public Rail N,E,S,W;
}
class Cart
{
public Dir D;
public Rail R;
public int Mem=0;
}
enum Dir {N=0,E=1,S=2,W=3}
void Main()
{
(List rails, List carts) = Parse(File.ReadAllLines(Path.Combine(Path.GetDirectoryName(Util.CurrentQueryPath), @"13_input.txt")));
for (int gen=0;;gen++)
{
foreach (var c in carts.OrderBy(c => c.R.Y*10000+c.R.X))
{
switch (c.D)
{
case Dir.S:
Move(c, new[] { (Dir.E, c.R.E), (Dir.S, c.R.S), (Dir.W, c.R.W) });
break;
case Dir.W:
Move(c, new[] { (Dir.S, c.R.S), (Dir.W, c.R.W), (Dir.N, c.R.N) });
break;
case Dir.N:
Move(c, new[] { (Dir.W, c.R.W), (Dir.N, c.R.N), (Dir.E, c.R.E) });
break;
case Dir.E:
Move(c, new[] { (Dir.N, c.R.N), (Dir.E, c.R.E), (Dir.S, c.R.S) });
break;
}
if (carts.Any(oc => oc != c && oc.R == c.R)) { $"{c.R.X},{c.R.Y} after {gen}".Dump(); return; }
}
//foreach (var c in carts) $"{c.R.X}|{c.R.Y}|{c.D}".Dump();"------".Dump();
}
}
void Move(Cart c, IEnumerable<(Dir, Rail)> options)
{
var outs = options.Where(p => p.Item2 != null).ToList();
if (outs.Count == 1)
{
c.R = outs[0].Item2;
c.D = outs[0].Item1;
}
else
{
c.R = outs[c.Mem % 3].Item2;
c.D = outs[c.Mem % 3].Item1;
c.Mem++;
}
}
void Dump(List rails, List carts)
{
int maxx = rails.Max(r => r.X) + 1;
int maxy = rails.Max(r => r.Y) + 1;
var b = new StringBuilder();
for (int yy = 0; yy < maxy; yy++)
{
for (int xx = 0; xx < maxx; xx++)
{
var cc = carts.FirstOrDefault(c => c.R.X == xx && c.R.Y == yy);
if (cc != null)
{
if (cc.D == Dir.N) b.Append('^');
if (cc.D == Dir.E) b.Append('>');
if (cc.D == Dir.S) b.Append('v');
if (cc.D == Dir.W) b.Append('<');
}
else if (rails.Any(r => r.X == xx && r.Y == yy))
{
b.Append('.');
}
else
{
b.Append(' ');
}
}
b.AppendLine();
}
b.ToString().Dump();
"".Dump();
}
(List, List) Parse(string[] line)
{
var rails = new Dictionary<(int,int), Rail>();
var carts = new List();
Rail get(int x, int y) { if(rails.TryGetValue((x,y), out var v))return v; Rail r = new Rail { X = x, Y = y }; rails.Add((x,y),r); return r; }
char last = ' ';
for (int y = 0; y < line.Length; y++)
{
last = ' ';
for (int x = 0; x < line[y].Length; x++)
{
char c = line[y][x];
if (c==' ') continue;
switch (c)
{
case '-':
{
var rr = get(x, y);
var ra = get(x - 1, y);
var rb = get(x + 1, y);
rr.W = ra; ra.E = rr;
rr.E = rb; rb.W = rr;
}
break;
case '|':
{
var rr = get(x, y);
var ra = get(x, y - 1);
var rb = get(x, y + 1);
rr.N = ra; ra.S = rr;
rr.S = rb; rb.N = rr;
}
break;
case '+':
{
var rr = get(x, y);
var ra = get(x, y - 1);
var rb = get(x + 1, y);
var rc = get(x, y + 1);
var rd = get(x - 1, y);
rr.N = ra; ra.S = rr;
rr.E = rb; rb.W = rr;
rr.S = rc; rc.N = rr;
rr.W = rd; rd.E = rr;
}
break;
case '/':
if (last == '-' || last == '+')
{
var rr = get(x, y);
var ra = get(x - 1, y);
var rb = get(x, y - 1);
rr.W = ra; ra.E = rr;
rr.N = rb; rb.S = rr;
}
else
{
var rr = get(x, y);
var ra = get(x + 1, y);
var rb = get(x, y + 1);
rr.E = ra; ra.W = rr;
rr.S = rb; rb.N = rr;
}
break;
case '\\':
if (last == '-' || last == '+')
{
var rr = get(x, y);
var ra = get(x - 1, y);
var rb = get(x, y + 1);
rr.W = ra; ra.E = rr;
rr.S = rb; rb.N = rr;
}
else
{
var rr = get(x, y);
var ra = get(x + 1, y);
var rb = get(x, y - 1);
rr.E = ra; ra.W = rr;
rr.N = rb; rb.S = rr;
}
break;
case '^':
{
var rr = get(x, y);
var ra = get(x, y - 1);
var rb = get(x, y + 1);
rr.N = ra; ra.S = rr;
rr.S = rb; rb.N = rr;
carts.Add(new Cart { D = Dir.N, R=rr, });
}
break;
case 'v':
{
var rr = get(x, y);
var ra = get(x, y - 1);
var rb = get(x, y + 1);
rr.N = ra; ra.S = rr;
rr.S = rb; rb.N = rr;
carts.Add(new Cart { D = Dir.S, R=rr, });
}
break;
case '>':
{
var rr = get(x, y);
var ra = get(x - 1, y);
var rb = get(x + 1, y);
rr.W = ra; ra.E = rr;
rr.E = rb; rb.W = rr;
carts.Add(new Cart { D = Dir.E, R = rr, });
}
break;
case '<':
{
var rr = get(x, y);
var ra = get(x - 1, y);
var rb = get(x + 1, y);
rr.W = ra; ra.E = rr;
rr.E = rb; rb.W = rr;
carts.Add(new Cart { D = Dir.W, R = rr, });
}
break;
}
last = c;
}
}
return (rails.Select(p=>p.Value).ToList(), carts);
}