day 8

Day8.cs

@@ -0,0 +1,39 @@
+using aoc2019.lib;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace aoc2019
+{
+    internal class Day8 : Day
+    {
+        public override int DayNumber => 8;
+
+        private readonly List<List<char>> photo;
+        public Day8()
+        {
+            photo = Input.First().Chunk(25 * 6).Select(s => s.ToList()).ToList();
+        }
+
+        public override string Part1()
+        {
+            var l = photo.OrderBy(layer => layer.Count(pixel => pixel == '0')).First();
+            return $"{l.Count(p => p == '1') * l.Count(p => p == '2')}";
+        }
+
+        public override string Part2()
+        {
+            return Enumerable.Range(0, 25 * 6)
+                .Select(p => Enumerable.Range(0, photo.Count)
+                    .Select(l => photo[l][p])
+                    .Aggregate('2', (acc, next) =>
+                        acc != '2' ? acc : next == '0' ? ' ' : next
+                    )
+                )
+                .ToDelimitedString()
+                .Chunk(25)
+                .ToDelimitedString(Environment.NewLine)
+                .Replace('1', 'x');
+        }
+    }
+}

aoc2019.csproj

@@ -27,6 +27,9 @@
     <None Update="input\day7.in">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="input\day8.in">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>

lib/Extensions.cs

@@ -11,5 +11,16 @@ namespace aoc2019.lib
             if (list.Count() == 1) return new[] { list };
             return list.SelectMany(t => Permute(list.Where(x => !x.Equals(t))), (v, p) => p.Prepend(v));
         }
+
+        public static IEnumerable<string> Chunk(this string str, int chunkSize)
+        {
+            for (int i = 0; i < str.Length; i += chunkSize)
+                yield return str.Substring(i, chunkSize);
+        }
+
+        public static string ToDelimitedString<T>(this IEnumerable<T> enumerable, string delimiter = "")
+        {
+            return string.Join(delimiter, enumerable);
+        }
     }
 }