1 files changed, 102 insertions, 0 deletions
diff --git a/Day14.cs b/Day14.cs
new file mode 100644
index 0000000..99e28e0
--- /dev/null
+++ b/Day14.cs
@@ -0,0 +1,102 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace aoc2019
+{
+    internal class Day14 : Day
+    {
+        public override int DayNumber => 14;
+
+        private Dictionary<string, long> available;
+        private readonly Dictionary<string, Reaction> reactions;
+
+        private struct Component
+        {
+            public string Name { get; set; }
+            public int Quantity { get; set; }
+        }
+
+        private class Reaction
+        {
+            public Component product;
+            public Component[] reactants;
+
+            public Reaction(Component[] reactants, Component product)
+            {
+                this.reactants = reactants;
+                this.product = product;
+            }
+
+            public static Reaction Parse(string s)
+            {
+                var ss = s.Split(new[] { ", ", " => " }, System.StringSplitOptions.None);
+
+                return new Reaction(
+                    ss.Take(ss.Length - 1).Select(ParseComponent).ToArray(),
+                    ParseComponent(ss[^1])
+                );
+
+                static Component ParseComponent(string s)
+                {
+                    var i = s.IndexOf(' ');
+                    return new Component
+                    {
+                        Name = s[(i + 1)..],
+                        Quantity = int.Parse(s.Substring(i))
+                    };
+                }
+            }
+        }
+
+        private bool Consume(string chem, long quantity)
+        {
+            if (quantity <= 0)
+                throw new ArgumentOutOfRangeException();
+
+            if (!available!.ContainsKey(chem))
+                available[chem] = 0;
+
+            if (available[chem] < quantity && !Produce(chem, quantity - available[chem]))
+                return false;
+
+            available[chem] -= quantity;
+            return true;
+        }
+
+        private bool Produce(string chem, long quantity)
+        {
+            if (chem == "ORE")
+                return false;
+
+            var reaction = reactions[chem];
+            var reactionCount = (long)Math.Ceiling((double)quantity / reaction.product.Quantity);
+
+            foreach (var reactant in reaction.reactants)
+                if (!Consume(reactant.Name, reactionCount * reactant.Quantity))
+                    return false;
+
+            available![chem] = available.GetValueOrDefault(chem) + reactionCount * reaction.product.Quantity;
+            return true;
+        }
+
+        public Day14()
+        {
+            reactions = Input
+                .Select(Reaction.Parse)
+                .ToDictionary(r => r.product.Name);
+        }
+
+        public override string Part1()
+        {
+            available = new Dictionary<string, long> { { "ORE", long.MaxValue } };
+            Consume("FUEL", 1);
+            return $"{long.MaxValue - available["ORE"]}";
+        }
+
+        public override string Part2()
+        {
+            return "";
+        }
+    }
+}