feat: solve part 1 and part 2

2023-12-16 20:36:09 -06:00
parent 578681451b
commit e7af72913a
4 changed files with 320 additions and 12 deletions
@@ -1,2 +1,171 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+using System.Diagnostics;
+
+namespace CosmicExpansion;
+
+public class Program
+{
+  public static async Task<int> Main(string[] args)
+  {
+    if (args.Length is 0)
+    {
+      Console.WriteLine("Please provide a path to the input file.");
+      return -1;
+    }
+
+    if (File.Exists(args[0]) is false)
+    {
+      Console.WriteLine("The provided file does not exist.");
+      return -2;
+    }
+
+    var isPart2 = args.Length > 1 && args[1] == "part2";
+    var input = await File.ReadAllLinesAsync(args[0]);
+
+    var stopwatch = new Stopwatch();
+    stopwatch.Start();
+
+    var universe = isPart2
+      ? Universe.Parse(input, 1_000_000)
+      : Universe.Parse(input);
+
+    var result = universe.SumOfShortestPathsBetweenGalaxies;
+
+    stopwatch.Stop();
+
+    Console.WriteLine($"The sum of the shortest paths between galaxies is {result}. ({stopwatch.ElapsedMilliseconds}ms)");
+
+    return (int)result;
+  }
+}
+
+public class Universe(
+  int height,
+  int width,
+  List<Galaxy> galaxies
+)
+{
+  private const char GalaxySymbol = '#';
+  public int Height { get; init; } = height;
+  public int Width { get; init; } = width;
+  public List<Galaxy> Galaxies { get; init; } = galaxies;
+  public long SumOfShortestPathsBetweenGalaxies =>
+    GetShortestPathsBetweenGalaxies()
+    .Values
+    .Sum();
+
+  public Dictionary<(int galaxyOneIndex, int galaxyTwoIndex), long> GetShortestPathsBetweenGalaxies()
+  {
+    var shortestPaths = new Dictionary<(int galaxyOneIndex, int galaxyTwoIndex), long>();
+
+    for (int i = 0; i < Galaxies.Count; i++)
+    {
+      var galaxyOne = Galaxies[i];
+
+      for (int j = i + 1; j < Galaxies.Count; j++)
+      {
+        var galaxyTwo = Galaxies[j];
+
+        if (shortestPaths.ContainsKey((i, j)) || shortestPaths.ContainsKey((j, i)))
+        {
+          continue;
+        }
+
+        var shortestPath = CalculateDistanceBetweenGalaxies(galaxyOne, galaxyTwo);
+        shortestPaths.Add((i, j), shortestPath);
+      }
+    }
+
+    return shortestPaths;
+  }
+
+  public static long CalculateDistanceBetweenGalaxies(Galaxy galaxyOne, Galaxy galaxyTwo) =>
+    Math.Abs(galaxyTwo.Row - galaxyOne.Row) + Math.Abs(galaxyTwo.Column - galaxyOne.Column);
+
+  public static Universe Parse(string[] input, int expandFactor = 2)
+  {
+    var emptyRows = new List<int>();
+    var emptyColumns = new List<int>();
+    var galaxies = new List<Galaxy>();
+
+    for (int i = 0; i < input.Length; i++)
+    {
+      var currentRow = input[i];
+
+      if (currentRow.Contains(GalaxySymbol) is false)
+      {
+        emptyRows.Add(i);
+      }
+    }
+
+    for (int i = 0; i < input[0].Length; i++)
+    {
+      var galaxyInColumn = false;
+
+      for (int j = 0; j < input.Length; j++)
+      {
+        var currentPosition = input[j][i];
+
+        if (currentPosition == GalaxySymbol)
+        {
+          galaxyInColumn = true;
+          break;
+        }
+      }
+
+      if (galaxyInColumn is false)
+      {
+        emptyColumns.Add(i);
+      }
+    }
+
+    for (int i = 0; i < input.Length; i++)
+    {
+      var currentRow = input[i];
+
+      for (int j = 0; j < currentRow.Length; j++)
+      {
+        var currentPosition = currentRow[j];
+
+        if (currentPosition == GalaxySymbol)
+        {
+          var numOfEmptyRowsBefore = emptyRows.Where(row => row < i).Count();
+          var rowOffset = numOfEmptyRowsBefore is 0
+            ? 0
+            : (numOfEmptyRowsBefore * expandFactor) - numOfEmptyRowsBefore;
+
+          var numOfEmptyColumnsBefore = emptyColumns.Where(column => column < j).Count();
+          var columnOffset = numOfEmptyColumnsBefore is 0
+            ? 0
+            : (numOfEmptyColumnsBefore * expandFactor) - numOfEmptyColumnsBefore;
+
+          galaxies.Add(new Galaxy(i + rowOffset, j + columnOffset));
+        }
+      }
+    }
+
+    var heightOffset = emptyRows.Count is 0
+      ? 0
+      : (emptyRows.Count * expandFactor) - emptyRows.Count;
+    var widthOffset = emptyColumns.Count is 0
+      ? 0
+      : (emptyColumns.Count * expandFactor) - emptyColumns.Count;
+
+    var height = input.Length + heightOffset;
+    var width = input[0].Length + widthOffset;
+
+    return new Universe(
+      height,
+      width,
+      galaxies
+    );
+  }
+}
+
+public class Galaxy(
+  long row,
+  long column
+)
+{
+  public long Row { get; init; } = row;
+  public long Column { get; init; } = column;
+}