feat(*): Add 2021-14 files (part 1 not working, part 2 not attempted)

2021/14/Program.cs

@@ -0,0 +1,104 @@
+namespace Day14
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            string[] lines = File.ReadAllLines("input.txt");
+
+
+            Part1(lines);
+            //Part2(lines);
+        }
+
+        static void Part1(string[] lines)
+        {
+            string polymerTemplate = lines[0];
+
+            Console.WriteLine($"Template: {polymerTemplate}");
+
+            // Pair insertion rules are stored from index 2 onwards
+            // A rule like AB -> C means that when elements A and B are immediately adjacent, element C
+            // should be inserted between them.
+            // Also, because all pairs are considered simultaneously, inserted elements are not considered
+            // to be part of a pair until the next step.
+
+            List<Rule> rules = new List<Rule>();
+            // Consider each rule
+            for (int i = 2; i < lines.Length; i++)
+            {
+                // e.g. AB -> C
+                string pairToMatch = lines[i].Substring(0, 2);
+                string characterToInsert = lines[i].Substring(6, 1);
+
+                rules.Add(new Rule()
+                {
+                    First = pairToMatch[0],
+                    Second = pairToMatch[1],
+                    Insert = characterToInsert[0],
+                });
+            }
+
+            // Set the number of steps to run (1 lower than expected due to 0 indexing)
+            for (int i = 0; i < 9; i++)
+            {
+                CompleteStep(ref polymerTemplate, ref lines, rules);
+                //Console.WriteLine($"After step {i+1}: {polymerTemplate}");
+            }
+
+            // Count occurrences of each character
+            char[] chars = polymerTemplate.ToCharArray();
+            List<char> uniqueCharacters = chars.Select(x => x).Distinct().ToList();
+            List<(char character, int count)> countList = new List<(char character, int count)>();
+
+            foreach (char character in uniqueCharacters)
+            {
+                countList.Add((character, polymerTemplate.Count(c => c == character)));
+            }
+
+            (char character, int count) mostCommon = countList.MaxBy(x => x.count);
+            (char character, int count) leastCommon = countList.MinBy(x => x.count);
+
+            Console.WriteLine(mostCommon.count - leastCommon.count);
+        }
+
+        static void CompleteStep(ref string polymerTemplate, ref string[] lines, List<Rule> rules)
+        {
+            LinkedList<char> temporaryList = new LinkedList<char>();
+            List<char> temporaryTemplate = new List<char>();
+
+            foreach (char character in polymerTemplate)
+            {
+                temporaryList.AddLast(character);
+                temporaryTemplate.Add(character);
+            }
+
+            LinkedListNode<char> pointer = temporaryList.Find(temporaryList.First());
+
+            // Insert the new character into the linked list but do not change the temporary template we're checking against
+            for (int i = 0; i < temporaryTemplate.Count() - 1; i++)
+            {
+                Rule matchingRule = rules.FirstOrDefault(r => r.First == temporaryTemplate.ElementAt(i) && r.Second == temporaryTemplate.ElementAt(i + 1));
+
+                if (matchingRule is not null)
+                {
+                    temporaryList.AddAfter(pointer, matchingRule.Insert);
+
+                    // Move on an extra position as we have added a node
+                    pointer = pointer.Next;
+                }
+
+                pointer = pointer.Next;
+            }
+
+            polymerTemplate = String.Join("", temporaryList);
+        }
+
+        class Rule
+        {
+            public char First { get; set; }
+            public char Second { get; set; }
+            public char Insert { get; set; }
+        }
+    }
+}