Day 6

2020.csproj

@@ -22,6 +22,9 @@
     <None Update="05input.txt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="06input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>

Program.cs

@@ -9,6 +9,7 @@
          Q03.Go();
          Q04.Go();
          Q05.Go();
+         Q06.Go();
       }
    }
 }

Q06.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+
+namespace _2020
+{
+   class Q06
+   {
+      class group
+      {
+         public int numInGroup;
+         public Dictionary<char, int> answers;
+      }
+      static List<group> list = new List<group>();
+
+      public static void Go()
+      {
+         MakeList();
+         Part1();
+         Part2();
+      }
+
+      static void MakeList()
+      {
+         using var fs = new FileStream("06input.txt", FileMode.Open);
+         using var sr = new StreamReader(fs);
+         string line;
+         group entry = null;
+         while ((line = sr.ReadLine()) != null)
+         {
+            if (line.Length == 0 || entry == null)
+            {
+               entry = new group()
+               {
+                  numInGroup = 0,
+                  answers = new Dictionary<char, int>(),
+               };
+               list.Add(entry);
+            }
+
+            if (line.Length == 0)
+            {
+               continue;
+            }
+
+            entry.numInGroup++;
+            foreach (var ch in line)
+            {
+               if (!entry.answers.ContainsKey(ch))
+               {
+                  entry.answers.Add(ch, 1);
+               }
+               else
+               {
+                  entry.answers[ch]++;
+               }
+            }
+         }
+      }
+
+      static void Part1()
+      {
+         var sum = list.Sum(x => x.answers.Keys.Count);
+         Debug.WriteLine($"Q06Part1: sum={sum}");
+      }
+
+      static void Part2()
+      {
+         var sum = list.Sum(x => x.answers.Sum(y => y.Value == x.numInGroup ? 1 : 0));
+         Debug.WriteLine($"Q06Part2: sum={sum}");
+      }
+   }
+}