part two completed somehow

AdventOfCode2025/Lobby.cs

@@ -8,10 +8,13 @@ public class Lobby : IAdventSolution
     public AdventSolution Solve(string input)
     {
         var lines = input.SplitLines();
-        var total = 0;
+        var total = 0UL;
+        var total2 = 0UL;
         foreach (var line in lines)
         {
-            var first = '0';
+            total += GreatestXDigits(line, 2);
+            total2 += GreatestXDigits(line, 12);
+            /*var first = '0';
             var second = '0';
             for (var i = 0; i < line.Length; i++)
             {
@@ -25,11 +28,41 @@ public class Lobby : IAdventSolution
                     second = line[i];
                 }
             }
-            
+            total += int.Parse($"{first}{second}");*/
-            
-            total += int.Parse($"{first}{second}");
         }
         
-        return new AdventSolution(total.ToString(), null);
+        return new AdventSolution(total.ToString(), total2.ToString());
+    }
+
+    private readonly List<char> _chars = new();
+
+    private ulong GreatestXDigits(string input, int digits)
+    {
+        _chars.Clear();
+        _chars.Add(input[0]);
+        for (var i = 1; i < input.Length; i++)
+        {
+            var remainingChars = input.Length - i - 1;
+            var c = input[i];
+            if(!IsReplace(c, remainingChars, digits) && _chars.Count < digits)
+            {
+                _chars.Add(c);
+            }
+        }
+        
+        return ulong.Parse(string.Join("", _chars));
+    }
+
+    private bool IsReplace(char c, int remaining, int digits)
+    {
+        for (var i = 0; i < _chars.Count; i++)
+        {
+            if (c <= _chars[i] || (remaining < digits - (i+1))) continue;
+            _chars.RemoveRange(i, _chars.Count - i);
+            _chars.Add(c);
+            return true;
+        }
+
+        return false;
     }
 }