feat: solved day 2 part 1...part 2 is WIP

02/RedNosedReports/Direction.cs

@@ -0,0 +1,8 @@
+namespace RedNosedReports;
+
+static class Direction
+{
+  public const string Unknown = "Unknown";
+  public const string Increasing = "Increasing";
+  public const string Decreasing = "Decreasing";
+}

02/RedNosedReports/Program.cs

@@ -0,0 +1,30 @@
+using System.Diagnostics;
+
+using RedNosedReports;
+
+if (args.Length is 0)
+{
+  Console.WriteLine("Please provide a path to the input file.");
+  return;
+}
+
+if (File.Exists(args[0]) is false)
+{
+  Console.WriteLine("The provided file does not exist.");
+  return;
+}
+
+var isPart2 = args.Length is 2 && args[1] is "part2";
+var input = await File.ReadAllLinesAsync(args[0]);
+
+var stopwatch = new Stopwatch();
+stopwatch.Start();
+
+var reports = new PuzzleParser().Parse(input);
+
+var numberOfSafeReports = isPart2
+  ? reports.Count(r => r.IsSafeWithProblemDampener())
+  : reports.Count(r => r.IsSafe());
+
+stopwatch.Stop();
+Console.WriteLine($"The total number of safe reports is {numberOfSafeReports}. ({stopwatch.ElapsedMilliseconds}ms)");

02/RedNosedReports/PuzzleParser.cs

@@ -0,0 +1,17 @@
+namespace RedNosedReports;
+
+class PuzzleParser
+{
+  public List<Report> Parse(string[] lines)
+  {
+    var reports = new List<Report>();
+
+    foreach (var line in lines)
+    {
+      var numbers = line.Split(' ').Select(int.Parse).ToList();
+      reports.Add(new Report(numbers));
+    }
+
+    return reports;
+  }
+}

02/RedNosedReports/RedNosedReports.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <NoWarn>CA1822</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="$(AssemblyName).Tests" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="..\INPUT.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+</Project>

02/RedNosedReports/Report.cs

@@ -0,0 +1,81 @@
+namespace RedNosedReports;
+
+class Report(List<int> levels)
+{
+  private readonly List<int> _levels = levels;
+
+  public bool IsSafe()
+  {
+    for (var i = 0; i < _levels.Count - 1; i++)
+    {
+      if (CheckIfSafe(_levels[i], _levels[i + 1]) is false)
+      {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  public bool IsSafeWithProblemDampener()
+  {
+    for (var currentIndex = 0; currentIndex < _levels.Count - 1; currentIndex++)
+    {
+      var nextIndex = currentIndex + 1;
+      var current = _levels[currentIndex];
+      var next = _levels[nextIndex];
+
+      if (CheckIfSafe(current, next) is false)
+      {
+        var levelsWithoutCurrent = _levels.ToList();
+        levelsWithoutCurrent.RemoveAt(currentIndex);
+        var isSafeWithoutCurrent = new Report(levelsWithoutCurrent).IsSafe();
+
+        if (isSafeWithoutCurrent)
+        {
+          return true;
+        }
+
+        var levelsWithoutNext = _levels.ToList();
+        levelsWithoutNext.RemoveAt(nextIndex);
+        var isSafeWithoutNext = new Report(levelsWithoutNext).IsSafe();
+
+        if (isSafeWithoutNext)
+        {
+          return true;
+        }
+
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  private bool CheckIfSafe(int current, int next)
+  {
+    var direction = _levels[1] > _levels[0]
+      ? Direction.Increasing
+      : Direction.Decreasing;
+
+    var isNextGreaterThanCurrent = next > current;
+    var delta = Math.Abs(next - current);
+
+    if (delta > 3 || delta < 1)
+    {
+      return false;
+    }
+
+    if (direction is Direction.Increasing && isNextGreaterThanCurrent is false)
+    {
+      return false;
+    }
+
+    if (direction is Direction.Decreasing && isNextGreaterThanCurrent)
+    {
+      return false;
+    }
+
+    return true;
+  }
+}