day 5 part 1

AdventOfCode/Day05.cs

@@ -0,0 +1,89 @@
+namespace AdventOfCode;
+
+internal class Day05 : BaseDay
+{
+    private readonly Dictionary<int, List<int>> rules = new Dictionary<int, List<int>>();
+    private readonly Dictionary<int, List<int>> rulesReversed = new Dictionary<int, List<int>>();
+    private readonly List<List<int>> updates = new List<List<int>>();
+
+    public Day05()
+    {
+        string[] lines = File.ReadAllLines(InputFilePath);
+
+        bool isRule = true;
+        foreach (string line in lines)
+        {
+            if (line == string.Empty)
+            {
+                isRule = false;
+                continue;
+            }
+            if (isRule)
+            {
+                string[] ruleParts = line.Split('|');
+                int left = int.Parse(ruleParts[0]);
+                int right = int.Parse(ruleParts[1]);
+
+                if (!rules.TryAdd(left, new List<int> { right }))
+                {
+                    rules[left].Add(right);
+                }
+
+                if (!rulesReversed.TryAdd(right, new List<int> { left }))
+                {
+                    rulesReversed[right].Add(left);
+                }
+            }
+            else 
+            {
+                updates.Add(line.Split(',').Select(int.Parse).ToList());
+            }
+        }
+    }
+
+    public override ValueTask<string> Solve_1()
+    {
+        int result = 0;
+        foreach (var update in updates)
+        {
+            if (IsCorrectOrder(update))
+            {
+                int middle = update.Skip(update.Count / 2).First();
+                result += middle;
+            }
+        }
+
+        return new(result.ToString());
+    }
+
+    public override ValueTask<string> Solve_2()
+    {
+        return new("");
+    }
+
+    private bool IsCorrectOrder(List<int> update)
+    {
+        for(int i = 0; i < update.Count; ++i)
+        {
+            if (rules.TryGetValue(update[i], out List<int> haveToBeToTheRight))
+            {
+                var toTheLeft = update.Take(i).ToList();
+                if (toTheLeft.Intersect(haveToBeToTheRight).Any())
+                {
+                    return false;
+                }
+            }
+
+            if (rulesReversed.TryGetValue(update[i], out List<int> haveToBeToTheLeft))
+            {
+                var toTheRight = update.Skip(i+1).ToList();
+                if (toTheRight.Intersect(haveToBeToTheLeft).Any())
+                {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+}