day(19): Linen Layout 🧦

src/AdventOfCode/Day19.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace AdventOfCode
+{
+    /// <summary>
+    /// Solver for Day 19
+    /// </summary>
+    public class Day19
+    {
+        public int Part1(string[] input)
+        {
+            string[] allowed = input[0].Split(", ");
+            var cache = new Dictionary<string, bool>();
+            return input.Skip(2).Count(i => Possible(i, allowed, cache));
+        }
+
+        public long Part2(string[] input)
+        {
+            string[] allowed = input[0].Split(", ");
+            var cache = new Dictionary<string, long>();
+            return input.Skip(2).Sum(i => Possible2(i, allowed, cache));
+        }
+
+        private static bool Possible(string check, string[] allowed, Dictionary<string, bool> cache)
+        {
+            if (check.Length == 0)
+            {
+                return true;
+            }
+
+            if (cache.TryGetValue(check, out bool result)) return result;
+
+            result = allowed.Where(a => a.Length <= check.Length)
+                            .Where(check.StartsWith)
+                            .Any(a => Possible(check[a.Length..], allowed, cache));
+
+            cache[check] = result;
+            return result;
+        }
+
+        private static long Possible2(string check, string[] allowed, Dictionary<string, long> cache)
+        {
+            if (check.Length == 0)
+            {
+                return 1;
+            }
+
+            if (cache.TryGetValue(check, out long result)) return result;
+
+            result = allowed.Where(a => a.Length <= check.Length)
+                            .Where(check.StartsWith)
+                            .Sum(a => Possible2(check[a.Length..], allowed, cache));
+
+            cache[check] = result;
+            return result;
+        }
+    }
+}

tests/AdventOfCode.Tests/Day19Tests.cs

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+using System.IO;
+using Xunit;
+using Xunit.Abstractions;
+
+
+namespace AdventOfCode.Tests
+{
+    public class Day19Tests
+    {
+        private readonly ITestOutputHelper output;
+        private readonly Day19 solver;
+
+        public Day19Tests(ITestOutputHelper output)
+        {
+            this.output = output;
+            this.solver = new Day19();
+        }
+
+        private static string[] GetRealInput()
+        {
+            string[] input = File.ReadAllLines("inputs/day19.txt");
+            return input;
+        }
+
+        private static string[] GetSampleInput()
+        {
+            return new string[]
+            {
+                "r, wr, b, g, bwu, rb, gb, br",
+                "",
+                "brwrr",
+                "bggr",
+                "gbbr",
+                "rrbgbr",
+                "ubwu",
+                "bwurrg",
+                "brgr",
+                "bbrgwb",
+            };
+        }
+
+        [Fact]
+        public void Part1_SampleInput_ProducesCorrectResponse()
+        {
+            var expected = 6;
+
+            var result = solver.Part1(GetSampleInput());
+
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public void Part1_RealInput_ProducesCorrectResponse()
+        {
+            var expected = 226;
+
+            var result = solver.Part1(GetRealInput());
+            output.WriteLine($"Day 19 - Part 1 - {result}");
+
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public void Part2_SampleInput_ProducesCorrectResponse()
+        {
+            var expected = 16;
+
+            var result = solver.Part2(GetSampleInput());
+
+            Assert.Equal(expected, result);
+        }
+
+        [Fact]
+        public void Part2_RealInput_ProducesCorrectResponse()
+        {
+            var expected = 601201576113503;
+
+            var result = solver.Part2(GetRealInput());
+            output.WriteLine($"Day 19 - Part 2 - {result}");
+
+            Assert.Equal(expected, result);
+        }
+    }
+}