2018 Day05 solved

Solutions/2018/Day05.cs

@@ -8,14 +8,35 @@ namespace AdventOfCode.Solutions._2018;
 /// </summary>
 [Description("Alchemical Reduction")]
 public sealed partial class Day05 {
-	private const int OFFSET = 'a' - 'A';
-
 	public static string Part1(string[] input, params object[]? _) => Solution1(input).ToString();
 	public static string Part2(string[] input, params object[]? _) => Solution2(input).ToString();
 
-	private static int Solution1(string[] input) {
+	private static int Solution1(string[] input)
+	{
+		return ReactPolymer(input[0]).Length;
+	}
+
+	private static int Solution2(string[] input)
+	{
 		string polymer = input[0];
+		int bestLength = int.MaxValue;
+
+		for (int i = 0; i < 26; i++) {
+			int length = ReactPolymer(polymer
+				.Replace(Convert.ToChar(i + 'a').ToString(), "")
+				.Replace(Convert.ToChar(i + 'A').ToString(), "")
+				).Length;
+			if (length < bestLength) {
+				bestLength = length;
+			}
+		}
 
+		return bestLength;
+	}
+
+	private static string ReactPolymer(string polymer)
+	{
+		const int OFFSET = 'a' - 'A';
 		int currentLength;
 		do {
 			StringBuilder newPolymer = new();
@@ -30,12 +51,6 @@ private static int Solution1(string[] input) {
 			polymer = newPolymer.ToString();
 		} while (polymer.Length != 0 && polymer.Length != currentLength);
 
-		return polymer.Length;
-	}
-
-	private static string Solution2(string[] input) {
-		//string inputLine = input[0];
-		//List<string> inputs = input.ToList();
-		return "** Solution not written yet **";
+		return polymer;
 	}
 }

Tests/2018/Tests_05.cs

@@ -17,7 +17,7 @@ public void Part1(string input, int expected)
 	}
 
 	[Theory]
-	[InlineData("aA", 9999)]
+	[InlineData("dabAcCaCBAcCcaDA", 4)]
 	public void Part2(string input, int expected)
 	{
 		_ = int.TryParse(SolutionRouter.SolveProblem(YEAR, DAY, PART2, input), out int actual);