feat: solve puzzle 3

2023-12-03 22:54:52 -06:00
parent 575b287b50
commit 19c35bc946
11 changed files with 777 additions and 19 deletions
@@ -1,2 +1,228 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+namespace GearRatios;
+
+public class Program
+{
+  public async static 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 puzzleSolver = new PuzzleSolver();
+
+    var input = await File.ReadAllLinesAsync(args[0]);
+    var result = args.Length > 1 && args[1] == "part2"
+      ? puzzleSolver.SumGearRatios(input)
+      : puzzleSolver.SumPartNumbers(input);
+
+    if (args.Length > 1 && args[1] == "part2")
+    {
+      Console.WriteLine($"The sum of all gear ratios is {result}.");
+    }
+    else
+    {
+      Console.WriteLine($"The sum of all part numbers is {result}.");
+    }
+
+    return result;
+  }
+}
+
+public class PuzzleSolver
+{
+  public int SumPartNumbers(string[] schematic)
+  {
+    var allPartNumbers = new List<int>();
+
+    for (var i = 0; i < schematic.Length; i++)
+    {
+      var currentLine = Line.Parse(schematic[i]);
+      var prevLine = i > 0 ? Line.Parse(schematic[i - 1]) : null;
+      var nextLine = i < schematic.Length - 1 ? Line.Parse(schematic[i + 1]) : null;
+      var linePartNumbers = currentLine.GetPartNumbers(prevLine, nextLine);
+      allPartNumbers.AddRange(linePartNumbers);
+    }
+
+    return allPartNumbers.Sum();
+  }
+
+  public int SumGearRatios(string[] schematic)
+  {
+    var allGearRatios = new List<int>();
+
+    for (var i = 0; i < schematic.Length; i++)
+    {
+      var currentLine = Line.Parse(schematic[i]);
+      var prevLine = i > 0 ? Line.Parse(schematic[i - 1]) : null;
+      var nextLine = i < schematic.Length - 1 ? Line.Parse(schematic[i + 1]) : null;
+      var lineGearRatios = currentLine.GetGearRatios(prevLine, nextLine);
+      allGearRatios.AddRange(lineGearRatios);
+    }
+
+    return allGearRatios.Sum();
+  }
+}
+
+public class Line(
+  List<Dictionary<int, Indexes>> numbers,
+  List<Dictionary<string, Indexes>> specialCharacters
+)
+{
+  public List<Dictionary<int, Indexes>> Numbers { get; init; } = numbers;
+  public List<Dictionary<string, Indexes>> SpecialCharacters { get; init; } = specialCharacters;
+  public List<int> SpecialCharacterIndexes => SpecialCharacters.SelectMany(dict => dict.Values).Select(v => v.Start).ToList();
+
+  private bool IsGearCharacter(string character) => character == "*";
+
+  public List<int> GetGearRatios(Line? previousLine = null, Line? nextLine = null)
+  {
+    var gearRatios = new List<int>();
+    var gearCharacters = SpecialCharacters.Where(dict => dict.Keys.Any(IsGearCharacter)).ToList();
+
+    if (previousLine is not null)
+    {
+      Numbers.AddRange(previousLine.Numbers);
+    }
+
+    if (nextLine is not null)
+    {
+      Numbers.AddRange(nextLine.Numbers);
+    }
+
+    foreach (var gear in gearCharacters)
+    {
+      foreach (var (key, value) in gear)
+      {
+        var beforeGear = value.Start - 1;
+        var afterGear = value.End + 1;
+
+        var gearNumbers = Numbers
+          .Where(
+            n => n.Values.Any(
+              v =>
+                v.Start >= beforeGear && v.Start <= afterGear ||
+                v.End >= beforeGear && v.End <= afterGear
+            )
+          )
+          .SelectMany(n => n.Keys)
+          .ToList();
+
+        if (gearNumbers.Count == 2)
+        {
+          gearRatios.Add(gearNumbers.First() * gearNumbers.Last());
+        }
+      }
+    }
+
+    return gearRatios;
+  }
+
+  public List<int> GetPartNumbers(Line? previousLine = null, Line? nextLine = null)
+  {
+    var partNumbers = new List<int>();
+
+    if (previousLine is not null)
+    {
+      SpecialCharacters.AddRange(previousLine.SpecialCharacters);
+    }
+
+    if (nextLine is not null)
+    {
+      SpecialCharacters.AddRange(nextLine.SpecialCharacters);
+    }
+
+    foreach (var number in Numbers)
+    {
+      foreach (var (key, value) in number)
+      {
+        var beforeNumber = value.Start - 1;
+        var afterNumber = value.End + 1;
+
+        if (SpecialCharacterIndexes.Any(idx => idx >= beforeNumber && idx <= afterNumber))
+        {
+          partNumbers.Add(key);
+        }
+      }
+    }
+
+    return partNumbers;
+  }
+
+  public static Line Parse(string line)
+  {
+    var numbers = new List<Dictionary<int, Indexes>>();
+    var specialCharacters = new List<Dictionary<string, Indexes>>();
+
+    var number = string.Empty;
+    int? numberStart = null;
+    int? numberEnd;
+
+    for (var i = 0; i < line.Length; i++)
+    {
+      var currentCharacter = line[i];
+
+      if (char.IsDigit(currentCharacter))
+      {
+        number += line[i];
+        numberStart ??= i;
+
+        if (i == line.Length - 1)
+        {
+          numberEnd = i;
+          numbers.Add(new()
+          {
+            {
+              int.Parse(number),
+              new Indexes(numberStart.Value, numberEnd.Value)
+            }
+          });
+        }
+      }
+      else
+      {
+        if (numberStart.HasValue)
+        {
+          numberEnd = i - 1;
+          numbers.Add(new()
+          {
+            {
+              int.Parse(number),
+              new Indexes(numberStart.Value, numberEnd.Value)
+            }
+          });
+          number = string.Empty;
+          numberStart = null;
+        }
+
+        if (currentCharacter == '.')
+        {
+          continue;
+        }
+
+        specialCharacters.Add(new()
+        {
+          {
+            currentCharacter.ToString(),
+            new Indexes(i, i)
+          }
+        });
+      }
+    }
+
+    return new Line(numbers, specialCharacters);
+  }
+}
+
+public class Indexes(int start, int end)
+{
+  public int Start { get; init; } = start;
+  public int End { get; init; } = end;
+}