feat(*): Add 2021-16 part 1 files not working

2026-07-13 03:03:46 +00:00 · 2021-12-16 09:32:14 +00:00
parent a727a69854
commit bef3eb551b
4 changed files with 221 additions and 1 deletions
@@ -0,0 +1,108 @@
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace Day16
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            string[] lines = File.ReadAllLines("input.txt");
+
+
+            Part1(lines);
+            //Part2(lines);
+        }
+
+        static void Part1(string[] lines)
+        {
+            string hex = lines[0];
+            string binary = Convert.ToString(Convert.ToInt32(hex, 16), 2);
+
+            List<int> versionNumbers = new List<int>();
+            List<int> outputList = new List<int>();
+
+            HandlePacket(ref versionNumbers, ref outputList, binary);
+
+            int total = versionNumbers.Sum(x => x);
+
+            Console.WriteLine($"The sum of version numbers in all packets is: {total}");
+        }
+
+        static void HandlePacket(ref List<int> versionNumbers, ref List<int> outputList, string binary)
+        {
+            int packetVersion = Convert.ToInt32(binary.Substring(0, 3), 2);
+            versionNumbers.Add(packetVersion);
+
+            int typeId = Convert.ToInt32(binary.Substring(3, 3), 2);
+
+            string remainingBinary = binary.Substring(6, binary.Length - 6);
+
+            if (typeId == 4)
+            {
+                // Packets represent a literal value
+                /*
+                 * Literal value packets encode a single binary number. To do this, the binary number 
+                 * is padded with leading zeroes until its length is a multiple of four bits, and then 
+                 * it is broken into groups of four bits. Each group is prefixed by a 1 bit except the last 
+                 * group, which is prefixed by a 0 bit. These groups of five bits immediately follow the packet header.
+                */
+                StringBuilder binaryLiteral = new StringBuilder();
+                string unprocessedBinary = string.Empty;
+
+                for (int i = 0; i < remainingBinary.Length; i += 5)
+                {
+                    binaryLiteral.Append(remainingBinary.Substring(i + 1, 4));
+
+                    if (remainingBinary[i] == '0')
+                    {
+                        // last group, end of packet
+                        unprocessedBinary = remainingBinary.Substring(i + 5, remainingBinary.Length - i);
+                        break;
+                    }
+                }
+
+                string binaryLiteralString = binaryLiteral.ToString();
+                int output = Convert.ToInt32(binaryLiteralString, 2);
+
+                outputList.Add(output);
+
+                // if the unprocessed binary doesn't just contain zeros process it again
+                if (!Regex.IsMatch(unprocessedBinary, @"^(0+)$"))
+                {
+                    HandlePacket(ref versionNumbers, ref outputList, unprocessedBinary);
+                }
+            }
+            else
+            {
+                // Packets represent an operator
+                char lengthTypeId = remainingBinary[0];
+
+                if (lengthTypeId == '0')
+                {
+                    // the next _15_ bits are a number that represents the _total length in bits_ of the
+                    // sub-packets contained by this packet.
+
+                    int totalLengthInBitsOfSubPacketsContainedByThisPacket = Convert.ToInt32(remainingBinary.Substring(1, 15), 2);
+
+                    string binaryToStillProcess = remainingBinary.Substring(16, totalLengthInBitsOfSubPacketsContainedByThisPacket);
+
+                    HandlePacket(ref versionNumbers, ref outputList, binaryToStillProcess);
+                }
+                else if (lengthTypeId == '1')
+                {
+                    // the next _11_ bits are a number that represents the _number of sub-packets
+                    // immediately contained_ by this packet.
+
+                    int numberOfSubPacketsImmediatelyContainedByThisPacket = Convert.ToInt32(remainingBinary.Substring(1, 11), 2);
+
+                    // TODO - I can't see how I can even use this information
+
+                    string binaryToStillProcess = remainingBinary.Substring(16, remainingBinary.Length - 16);
+
+                    HandlePacket(ref versionNumbers, ref outputList, binaryToStillProcess);
+                }
+            }
+        }
+    }
+}