From 2780eb7f831de5f655ed69d954a1447b256c271d Mon Sep 17 00:00:00 2001
From: Sander in 't Hout <sander@inthout.me>
Date: Fri, 20 Dec 2024 01:13:59 +0100
Subject: [PATCH] Add AoC 2024 day 19 part 1 solver

---
 assets/advent_of_code/2024_19_sample.txt      | 10 +++++
 .../advent_of_code/2024/_all_solvers.dart     |  1 +
 .../advent_of_code/2024/day_19_solver.dart    | 44 +++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 assets/advent_of_code/2024_19_sample.txt
 create mode 100644 lib/solvers/advent_of_code/2024/day_19_solver.dart

diff --git a/assets/advent_of_code/2024_19_sample.txt b/assets/advent_of_code/2024_19_sample.txt
new file mode 100644
index 0000000..ad43a74
--- /dev/null
+++ b/assets/advent_of_code/2024_19_sample.txt
@@ -0,0 +1,10 @@
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb
\ No newline at end of file
diff --git a/lib/solvers/advent_of_code/2024/_all_solvers.dart b/lib/solvers/advent_of_code/2024/_all_solvers.dart
index 1bdb038..324a720 100644
--- a/lib/solvers/advent_of_code/2024/_all_solvers.dart
+++ b/lib/solvers/advent_of_code/2024/_all_solvers.dart
@@ -13,3 +13,4 @@ export 'day_13_solver.dart';
 export 'day_14_solver.dart';
 export 'day_15_solver.dart';
 export 'day_17_solver.dart';
+export 'day_19_solver.dart';
diff --git a/lib/solvers/advent_of_code/2024/day_19_solver.dart b/lib/solvers/advent_of_code/2024/day_19_solver.dart
new file mode 100644
index 0000000..d093c66
--- /dev/null
+++ b/lib/solvers/advent_of_code/2024/day_19_solver.dart
@@ -0,0 +1,44 @@
+import 'package:darq/darq.dart';
+import 'package:h3x_devtools/solvers/advent_of_code/2024/aoc_2024_solver.dart';
+
+class Day19Solver extends AdventOfCode2024Solver {
+
+  @override
+  final int dayNumber = 19;
+
+  @override
+  String getSolution(String input) {
+    String splitNewline = input.contains('\r\n\r\n') ? '\r\n\r\n' : input.contains('\r\r') ? '\r\r' : '\n\n';
+    List<String> inputParts = input.split(splitNewline);
+
+    List<String> towelPatterns = inputParts[0].split(', ').toList();
+    List<String> desiredDesigns = inputParts[1].toListOfLines();
+
+    // Part 1 - First we filter all patterns that can't be composited themselves.
+    List<String> nonCompositablePatterns = [...towelPatterns];
+    for (String pattern in towelPatterns) {
+      nonCompositablePatterns.remove(pattern);
+      if (!_isDesignPossible('', pattern, nonCompositablePatterns)) nonCompositablePatterns.add(pattern);
+    }
+
+    // Now we check which designs are possible.
+    int possibleDesigns = desiredDesigns.where((design) => _isDesignPossible('', design, nonCompositablePatterns)).length;
+
+    return 'Possible designs: $possibleDesigns';
+  }
+
+  bool _isDesignPossible(String currentPattern, String desiredPattern, List<String> towelPatterns) {
+    for (String pattern in towelPatterns) {
+      String testingPattern = '$currentPattern$pattern';
+      if (testingPattern == desiredPattern) {
+        return true;
+      } else if (testingPattern.length < desiredPattern.length && desiredPattern.startsWith(testingPattern)) {
+        bool isPossible = _isDesignPossible(testingPattern, desiredPattern, towelPatterns);
+        if (isPossible) return true;
+      }
+    }
+
+    return false;
+  }
+
+}