advent24/Advent24/Day7.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection.Emit;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using System.IO.Compression;
using System.Xml.Serialization;

namespace Advent24
{
    internal class Day7
    {
        public Day7()
        {
            String fileData = System.IO.File.ReadAllText(@"..\..\..\inputd7.txt");

            String[] equations = fileData.Split('\n', StringSplitOptions.RemoveEmptyEntries);

            Int64 totalCalibrationResult = 0;

            Boolean concatenationEnabled = true;

            Int64 @base = concatenationEnabled ? 3 : 2;

            foreach (String equation in equations)
            {
                String[] subequation = equation.Split(':', StringSplitOptions.RemoveEmptyEntries);

                Int64 testValue = System.Convert.ToInt64(subequation[0]);

                String[] operands = subequation[1].Split(" ", StringSplitOptions.RemoveEmptyEntries);

                Int64[] intermediateResults = new Int64[(Int64)Math.Pow(@base, operands.Length-1)];

                Int64 intermediateResultIndex = (Int64)Math.Pow(@base, operands.Length - 1);

                Int64 numberOfSections = @base;

                Int64 sectionWidth = intermediateResults.Length / numberOfSections;

                Int64 operandIndex = 0;

                // copy first operand to all locations - half the total number of location will be to add the second operand, the other half will be to multiply it
                for(Int64 i = 0; i < intermediateResultIndex; i++)
                    intermediateResults[i] = System.Convert.ToInt64(operands[operandIndex]);
                
                operandIndex++;

                while (operandIndex < operands.Length)
                {
                    sectionWidth = intermediateResults.Length / numberOfSections;

                    for (Int64 sectionNumber = 0; sectionNumber < numberOfSections; sectionNumber++)


                        for (Int64 i = sectionNumber * sectionWidth; i < (sectionNumber + 1) * sectionWidth; i++)
                            if (sectionNumber % @base == 0)
                                // first choice of operator = +
                                intermediateResults[i] += System.Convert.ToInt64(operands[operandIndex]);
                            else if (sectionNumber % @base == 1)
                                // second choice of operator = *
                                intermediateResults[i] *= System.Convert.ToInt64(operands[operandIndex]);
                            else
                                // third choice of operator = || (concatenation)
                                intermediateResults[i] = intermediateResults[i] * (Int64)Math.Pow(10, operands[operandIndex].Length) + System.Convert.ToInt64(operands[operandIndex]);

                    numberOfSections *= @base;
                    operandIndex++;
                }

                if (intermediateResults.Contains(testValue))
                {
                    // testValue is possible
                    totalCalibrationResult += testValue;
                }
            }

            Console.WriteLine("totalCalibrationResult = {0:d}", totalCalibrationResult);

            // to keep the console window from closing
            Console.ReadKey();
        }
    }
}