feat: solve day 5 part 1

05/PrintQueue/OrderRule.cs

@@ -0,0 +1,3 @@
+namespace PrintQueue;
+
+record OrderRule(int X, int Y);

05/PrintQueue/ParseResult.cs

@@ -0,0 +1,3 @@
+namespace PrintQueue;
+
+record ParseResult(List<OrderRule> Rules, List<Update> Updates);

05/PrintQueue/Program.cs

@@ -1,5 +1,7 @@
 using System.Diagnostics;
 
+using PrintQueue;
+
 if (args.Length is 0)
 {
   Console.WriteLine("Please provide a path to the input file.");
@@ -13,14 +15,21 @@ if (File.Exists(args[0]) is false)
 }
 
 var isPart2 = args.Length is 2 && args[1] is "part2";
-var input = await File.ReadAllLinesAsync(args[0]);
+var input = await File.ReadAllTextAsync(args[0]);
 
 var stopwatch = new Stopwatch();
 stopwatch.Start();
 
-// TODO: Perform work here
-  
-stopwatch.Stop();
+var parser = new PuzzleParser();
 
-// TODO: Print results
-Console.WriteLine($". ({stopwatch.ElapsedMilliseconds}ms)");
+var parseResult = parser.Parse(input);
+
+var validator = new UpdateValidator(parseResult.Rules);
+
+var result = parseResult.Updates
+  .Where(u => validator.Validate(u))
+  .Select(u => u.GetMiddlePage())
+  .Sum();
+
+stopwatch.Stop();
+Console.WriteLine($"The sum of the page numbers is {result}. ({stopwatch.ElapsedMilliseconds}ms)");

05/PrintQueue/PuzzleParser.cs

@@ -0,0 +1,36 @@
+namespace PrintQueue;
+
+class PuzzleParser
+{
+  public ParseResult Parse(string input)
+  {
+    var inputParts = input.Split($"{Environment.NewLine}{Environment.NewLine}");
+    var rules = ParseRules(inputParts[0]);
+    var updates = ParseUpdates(inputParts[1]);
+    return new ParseResult(rules, updates);
+  }
+
+  private static List<Update> ParseUpdates(string input)
+  {
+    return input.Split(Environment.NewLine)
+      .Select(s => new Update(
+        s.Split(",").Select(int.Parse).ToList()
+      ))
+      .ToList();
+  }
+  
+  private static List<OrderRule> ParseRules(string input)
+  {
+    return input
+      .Split(Environment.NewLine)
+      .Select(s =>
+      {
+        var parts = s.Split("|");
+        return new OrderRule(
+          int.Parse(parts[0]),
+          int.Parse(parts[1])
+        );
+      })
+      .ToList();
+  }
+}

05/PrintQueue/Update.cs

@@ -0,0 +1,9 @@
+namespace PrintQueue;
+
+record Update(List<int> Pages)
+{
+  public int GetMiddlePage()
+  {
+    return Pages.Count is 0 ? 0 : Pages[Pages.Count / 2];
+  }
+}

05/PrintQueue/UpdateValidator.cs

@@ -0,0 +1,47 @@
+namespace PrintQueue;
+
+class UpdateValidator
+{
+  public readonly Dictionary<int, HashSet<int>> Graph = [];
+
+  public UpdateValidator(List<OrderRule> rules)
+  {
+    foreach (var rule in rules)
+    {
+      if (Graph.ContainsKey(rule.X) is false)
+      {
+        Graph.Add(rule.X, []);
+      }
+
+      if (Graph.ContainsKey(rule.Y) is false)
+      {
+        Graph.Add(rule.Y, []);
+      }
+      
+      Graph[rule.X].Add(rule.Y);
+    }
+  }
+  
+  public bool Validate(Update update)
+  {
+    var previousPages = new List<int>();
+    
+    foreach (var page in update.Pages)
+    {
+      foreach (var previousPage in previousPages)
+      {
+        if (
+          Graph.TryGetValue(previousPage, out HashSet<int>? value) &&
+          value.Contains(page) is false
+        )
+        {
+          return false;
+        }
+      }
+      
+      previousPages.Add(page);
+    }
+    
+    return true;
+  }
+}