Day 2: Red-Nosed Reports

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FAQ

  • Ananace@lemmy.ananace.dev
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    23 days ago

    Of course I ended up with a off-by-one error for the second part, so things took a bit longer than they really should’ve.

    But either way, behold, messy C#:

    C#
    int[][] reports = new int[0][];
    
    public void Input(IEnumerable<string> lines)
    {
      reports = lines.Select(l => l.Split(' ').Select(p => int.Parse(p)).ToArray()).ToArray();
    }
    
    public void Part1()
    {
      int safeCount = reports.Where(report => CheckReport(report)).Count();
      Console.WriteLine($"Safe: {safeCount}");
    }
    public void Part2()
    {
      int safeCount = reports.Where(report => {
        if (CheckReport(report))
          return true;
    
        for (int i = 0; i < report.Length; ++i)
          if (CheckReport(report.Where((_, j) => j != i)))
            return true;
    
        return false;
      }).Count();
    
      Console.WriteLine($"Safe: {safeCount}");
    }
    
    bool CheckReport(IEnumerable<int> report)
    {
      var diffs = report.SkipLast(1).Zip(report.Skip(1)).Select(v => v.Second - v.First);
      return diffs.All(v => Math.Abs(v) <= 3) && (diffs.All(v => v > 0) || diffs.All(v => v < 0));
    }