Day 7

Q07.cs

@@ -0,0 +1,128 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace _2020
+{
+   class Q07
+   {
+      class BagType
+      {
+         public string BagName;
+         public List<Tuple<string, int>> ValidContents = new List<Tuple<string, int>>();
+      }
+
+      static Regex bagRegex = new Regex(@"(?: contain |, )?(?<numBags>[0-9]+ )?(?<bagType>.+?) bags?", RegexOptions.Compiled);
+
+      static List<BagType> list = new List<BagType>();
+
+      public static void Go()
+      {
+         MakeList();
+         Part1();
+         Part2();
+      }
+
+      static void MakeList()
+      {
+         var lines = File.ReadAllLines("07input.txt");
+         foreach (var line in lines)
+         {
+            var matches = bagRegex.Matches(line);
+            if (matches.Count <= 1)
+            {
+               throw new Exception("Unexpected input line");
+            }
+
+            var bag = new BagType()
+            {
+               BagName = matches[0].Groups["bagType"].Value,
+            };
+
+            for (int i = 1; i < matches.Count; i++)
+            {
+               if (matches[i].Groups["bagType"].Value == "no other")
+               {
+                  break;
+               }
+
+               bag.ValidContents.Add(new Tuple<string, int>(matches[i].Groups["bagType"].Value, Convert.ToInt32(matches[i].Groups["numBags"].Value)));
+            }
+
+            list.Add(bag);
+         }
+      }
+
+      static List<BagType> GetBagsCanContain(BagType checkBag)
+      {
+         var retval = new List<BagType>();
+         foreach (var bag in list)
+         {
+            if (bag.ValidContents.FirstOrDefault(x => x.Item1 == checkBag.BagName) != null)
+            {
+               retval.Add(bag);
+            }
+         }
+
+         return retval;
+      }
+
+      static List<BagType> GetCanContainAny(List<BagType> others)
+      {
+         var retval = new List<BagType>();
+         foreach (var other in others)
+         {
+            retval.AddRange(GetBagsCanContain(other));
+         }
+
+         return retval;
+      }
+
+      static void Part1()
+      {
+         Func<List<string>, BagType, List<string>> bagAgg = (accum, bagType) =>
+         {
+            accum.Add(bagType.BagName);
+            return accum;
+         };
+
+         var directContain = GetBagsCanContain(new BagType() { BagName = "shiny gold" });
+         var totalContain = directContain.Aggregate(new List<string>(), bagAgg);
+
+         var recursiveContain = GetCanContainAny(directContain);
+         while (recursiveContain.Count > 0)
+         {
+            totalContain.AddRange(recursiveContain.Aggregate(new List<string>(), bagAgg));
+            recursiveContain = GetCanContainAny(recursiveContain);
+         }
+
+         var result = totalContain.Distinct();
+         Debug.WriteLine($"Q07Part1: total contain={result.Count()}");
+      }
+
+      static int GetNumBagsContainedIn(BagType bag)
+      {
+         int bagsNeeded = 0;
+         foreach (var contain in bag.ValidContents)
+         {
+            var containBagRule = list.First(x => x.BagName == contain.Item1);
+            bagsNeeded += contain.Item2;
+            bagsNeeded += contain.Item2 * GetNumBagsContainedIn(containBagRule);
+         }
+
+         return bagsNeeded;
+      }
+
+      static void Part2()
+      {
+         var shinyGoldBag = list.First(x => x.BagName == "shiny gold");
+
+         int bagsNeeded = GetNumBagsContainedIn(shinyGoldBag);
+
+         Debug.WriteLine($"Q07Part2: bags needed={bagsNeeded}");
+      }
+   }
+}