151 lines
3.4 KiB
C#
151 lines
3.4 KiB
C#
using System.Diagnostics;
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if (args.Length is 0)
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{
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Console.WriteLine("Please provide a path to the input file.");
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return;
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}
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if (File.Exists(args[0]) is false)
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{
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Console.WriteLine("The provided file does not exist.");
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return;
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}
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var isPart2 = args.Length is 2 && args[1] is "part2";
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var input = await File.ReadAllLinesAsync(args[0]);
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var stopwatch = new Stopwatch();
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stopwatch.Start();
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var map = TopoMap.From(input);
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// i'm going to to walk over the grid
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// i'm going to only worry about places where
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// there is a zero
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// need to check if we are on a nine
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// before we explore...also we should
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// be able to add to score here
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// when i encounter a zero i need to begin
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// exploring nearby tiles that increment by 1
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// in each left, right, up, down direction
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// any adj tile that fits this...is a tile i
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// need to also explore
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stopwatch.Stop();
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Console.WriteLine($". ({stopwatch.ElapsedMilliseconds}ms)");
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class TopoMap
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{
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private static Direction[] _directions = [
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Direction.Up,
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Direction.Down,
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Direction.Left,
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Direction.Right,
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];
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private readonly string[] _grid;
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private TopoMap(string[] input)
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{
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_grid = input;
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}
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public static TopoMap From(string[] input) => new(input);
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// TODO: This actually needs to be GetTrailHeadScore
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// I want to perform this search when I know I've reached
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// a trail head.
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public int GetTrailHeadScores()
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{
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var trailheadScore = 0;
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var visitedPositions = new HashSet<Position>();
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var positionsToVisit = new Queue<Position>();
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var startingX = 0;
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var startingY = 0;
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var startingHeight = int.Parse(_grid[startingY][startingX].ToString());
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positionsToVisit.Enqueue(new(startingX, startingY, startingHeight));
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while (positionsToVisit.Count != 0)
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{
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var currentPosition = positionsToVisit.Dequeue();
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if (visitedPositions.Contains(currentPosition))
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{
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continue;
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}
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visitedPositions.Add(currentPosition);
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if (currentPosition.Height is 9)
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{
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trailheadScore++;
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continue;
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}
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foreach (var direction in _directions)
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{
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if (currentPosition.TryGetNextPosition(direction, _grid, out var newPosition) is false)
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{
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continue;
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}
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if (visitedPositions.Contains(newPosition))
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{
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continue;
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}
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var heightDifference = newPosition.Height - currentPosition.Height;
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if (heightDifference is not 1)
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{
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continue;
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}
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positionsToVisit.Enqueue(newPosition);
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}
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}
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return trailheadScore;
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}
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}
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record Position(int X, int Y, int Height)
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{
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public bool TryGetNextPosition(Direction direction, string[] grid, out Position position)
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{
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var x = X + direction.XD;
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var y = Y + direction.YD;
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position = new(x, y, -1);
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var isOffGrid = IsOffGrid(position, grid);
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if (isOffGrid)
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{
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return false;
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}
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position = position with { Height = grid[y][x] };
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return true;
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}
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private bool IsOffGrid(Position position, string[] grid)
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{
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return position.X < 0 ||
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position.X > grid[0].Length - 1 ||
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position.Y > grid.Length - 1 ||
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position.Y < 0;
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}
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}
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record Direction(int XD, int YD)
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{
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public static Direction Up = new(0, -1);
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public static Direction Down = new(0, 1);
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public static Direction Left = new(-1, 0);
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public static Direction Right = new(1, 0);
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} |