day 6

Day6.cs

@@ -0,0 +1,39 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace aoc2019
+{
+    internal class Day6 : Day
+    {
+        public override int DayNumber => 6;
+
+        private readonly Dictionary<string, string> input;
+        public Day6()
+        {
+            input = Input.ToDictionary(i => i.Split(')')[1], i => i.Split(')')[0]);
+        }
+
+        private List<string> GetParents(string obj)
+        {
+            var res = new List<string>();
+            for (var curr = obj; curr != "COM"; curr = input[curr])
+                res.Add(curr);
+            res.Add("COM");
+            return res;
+        }
+
+        public override string Part1()
+        {
+            return $"{input.Keys.Sum(o => GetParents(o).Count - 1)}";
+        }
+
+        public override string Part2()
+        {
+            List<string> you = GetParents("YOU");
+            List<string> san = GetParents("SAN");
+            int common = 1;
+            for (; you[^common] == san[^common]; common++);
+            return $"{you.Count + san.Count - common * 2}";
+        }
+    }
+}

aoc2019.csproj

@@ -21,6 +21,9 @@
     <None Update="input\day5.in">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="input\day6.in">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>