Adv2018/D11.1/Program.cs

using System;

namespace D11._1
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length == 0) return;
            int serial = int.Parse(args[0]);

            const int length = 300;
            var grid = new int[length, length];

            for (int x = 1; x <= length; ++x)
            {
                for (int y = 1; y <= length; ++y)
                {
                    int id = (x + 10);

                    int n = (id * y + serial) * id;
                    int c = (n / 100) % 10;


                    grid[x - 1, y - 1] = c - 5;
                }
            }

            int maxTotal = 0;
            (int x, int y)? maxCoordinates = null;

            for (int x = 1; x <= length - 2; ++x)
            {
                for (int y = 1; y <= length - 2; ++y)
                {
                    int total = 0;
                    for (int j = 0; j < 3; ++j)
                    for (int i = 0; i < 3; ++i)
                        total += grid[x - 1 + i, y - 1 + j];

                    if (total > maxTotal)
                    {
                        maxTotal = total;
                        maxCoordinates = (x, y);
                    }
                }
            }

            Console.WriteLine($"The answer is : ({maxCoordinates.Value.x},{maxCoordinates.Value.y})");
        }
    }
}