initial commit, day 10
This commit is contained in:
Ikatono
238
dotnet/06/06.cs
Normal file
238
dotnet/06/06.cs
Normal file
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void Main1()
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{
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(var map, var pos) = LoadMap(Path.Join("..", "..", "06a.txt"));
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Guard guard = new(pos, Direction.North);
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HashSet<(int,int)> visited = new();
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while (map.InBounds(guard.position))
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{
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var next = Next(guard);
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if (map.Check(next.position))
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{
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guard = new(guard.position, guard.direction.Turn());
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continue;
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}
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else
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{
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visited.Add(guard.position);
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guard = next;
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}
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}
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Console.WriteLine(visited.Count());
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}
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void Main2()
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{
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(var map, var pos) = LoadMap(Path.Join("..", "..", "06a.txt"));
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Guard guard = new(pos, Direction.North);
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// for (int i = 0; i < 4; i++)
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// {
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// foreach (var obs in map.Obstacles)
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// {
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// var row = map.GetRow(obs.Item1 + 1).Where(c => c > obs.Item2);
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// foreach (var candidate in row)
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// {
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// var col = map.GetColumn(candidate - 1).Where(r => r > candidate);
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// foreach (var third in col)
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// {
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// var idea = (third - 1, obs.Item2 - 1);
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// if (!map.Check(idea))
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// map.Ideas.Add(idea);
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// }
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// }
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// }
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// map = map.Rotated();
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// }
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// Console.WriteLine($"Ideas {map.Ideas.Count()}");
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int count = 0;
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// foreach (var idea in map.Ideas)
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// {
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// Guard guard = new(pos, Direction.North);
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// // the 5th time the guard hits the obstacle, he must have hit twice from the same side
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// int hits = 0;
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// while (map.InBounds(guard.position))
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// {
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// var next = Next(guard);
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// if (next.position == idea)
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// {
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// hits++;
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// if (hits >= 5)
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// {
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// count++;
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// break;
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// }
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// guard = new(guard.position, guard.direction.Turn());
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// }
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// else if (map.Check(next.position))
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// {
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// guard = new(guard.position, guard.direction.Turn());
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// }
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// else
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// {
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// guard = next;
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// }
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// }
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// }
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HashSet<(int,int)> visited = new();
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int ideaIndex = 0;
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while (map.InBounds(guard.position))
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{
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ideaIndex++;
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var next = Next(guard);
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if (map.Check(next.position))
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{
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guard = new(guard.position, guard.direction.Turn());
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continue;
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}
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else
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{
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visited.Add(guard.position);
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if (!visited.Contains(next.position) && TestIdea(next.position, guard, map))
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count++;
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// Console.WriteLine($"Idea {ideaIndex}");
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guard = next;
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}
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}
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Console.WriteLine($"Solution {count}");
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}
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// Main1();
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Main2();
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(Map,(int,int)) LoadMap(string filename)
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{
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var lines = File.ReadAllLines(filename)
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.Where(s => !string.IsNullOrWhiteSpace(s))
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.ToList();
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var guard = (-1,-1);
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Map map = new();
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for (int i = 0; i < lines.Count(); i++)
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{
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for (int j = 0; j < lines[i].Count(); j++)
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{
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if (lines[i][j] == '#')
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map.Add((i, j));
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else if (lines[i][j] == '^')
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guard = (i, j);
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}
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}
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map.XBound = lines[0].Count();
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map.YBound = lines.Count();
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return (map, guard);
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}
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bool TestIdea((int,int) idea, Guard guard, Map map)
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{
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HashSet<Guard> history = new();
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while (map.InBounds(guard.position))
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{
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if (history.Contains(guard))
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return true;
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history.Add(guard);
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var next = Next(guard);
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if (map.Check(next.position) || next.position == idea)
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{
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guard = new(guard.position, guard.direction.Turn());
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}
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else
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{
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guard = next;
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}
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}
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return false;
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}
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//next position IF NO OBSTACLE
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Guard Next(Guard guard)
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{
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var pos = guard.position;
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return new(guard.direction switch
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{
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Direction.North => (pos.Item1-1, pos.Item2),
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Direction.East => (pos.Item1, pos.Item2+1),
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Direction.South => (pos.Item1+1, pos.Item2),
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Direction.West => (pos.Item1, pos.Item2-1),
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_ => throw new Exception(),
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}, guard.direction);
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}
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class Map
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{
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public HashSet<(int,int)> Obstacles = new();
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//1 greater than largest value
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public int XBound = 0;
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public int YBound = 0;
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public HashSet<(int,int)> Ideas = new();
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public Map()
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{
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}
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public void Add((int,int) obstacle)
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{
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Obstacles.Add(obstacle);
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}
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public bool Check((int,int) pos)
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{
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return Obstacles.Contains(pos);
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}
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public bool InBounds((int,int) pos)
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{
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return pos.Item1 >= 0 && pos.Item2 >= 0
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&& pos.Item1 < XBound && pos.Item2 < YBound;
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}
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//get list of columns with an obstacle in this row
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public List<int> GetRow(int row)
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{
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List<int> items = [];
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foreach (var pos in Obstacles)
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{
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if (pos.Item1 == row)
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items.Add(pos.Item2);
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}
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items.Sort();
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return items;
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}
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//get list of rows with an obstacle in this column
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public List<int> GetColumn(int column)
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{
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List<int> items = [];
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foreach (var pos in Obstacles)
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{
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if (pos.Item2 == column)
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items.Add(pos.Item1);
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}
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items.Sort();
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return items;
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}
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//counterclockwise rotation
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public Map Rotated()
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{
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(int,int) rotate((int,int) o) => (o.Item2, XBound - o.Item1);
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Map newmap = new();
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newmap.Obstacles = new(Obstacles.Select(rotate));
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newmap.Ideas = new(Ideas.Select(rotate));
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newmap.XBound = YBound;
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newmap.YBound = XBound;
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return newmap;
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}
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}
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enum Direction
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{
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North,
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East,
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South,
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West,
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}
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readonly record struct Guard((int,int) position, Direction direction);
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static class Extensions
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{
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public static Direction Turn(this Direction direction)
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{
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return direction switch
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{
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Direction.West => Direction.North,
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Direction d => d + 1,
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};
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}
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}
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