Euler_011.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Euler_11
{
    class Program
    {
        static void Main(string[] args)
        {
            int[][] grid = new int[20][];
            grid[00] = new int[]{08, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52, 12, 50, 77, 91, 08};
            grid[01] = new int[]{49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00};
            grid[02] = new int[]{81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65};
            grid[03] = new int[]{52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91};
            grid[04] = new int[]{22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80};
            grid[05] = new int[]{24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50};
            grid[06] = new int[]{32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70};
            grid[07] = new int[]{67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 08, 40, 91, 66, 49, 94, 21};
            grid[08] = new int[]{24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72};
            grid[09] = new int[]{21, 36, 23, 09, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95};
            grid[10] = new int[]{78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 09, 53, 56, 92};
            grid[11] = new int[]{16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57};
            grid[12] = new int[]{86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58};
            grid[13] = new int[]{19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40};
            grid[14] = new int[]{04, 52, 08, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66};
            grid[15] = new int[]{88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69};
            grid[16] = new int[]{04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 08, 46, 29, 32, 40, 62, 76, 36};
            grid[17] = new int[]{20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16};
            grid[18] = new int[]{20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54};
            grid[19] = new int[]{01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48};
            
            int max = -1;
            for (int i=0; i<20; i++)
            {
                for (int j=0; j<20; j++)
                {
                    if (i+3<=19)
                        max = Math.Max(grid[i][j]*
                                       grid[i+1][j]*
                                       grid[i+2][j]*
                                       grid[i+3][j], max);
                    
                    if (j+3<=19)
                        max = Math.Max(grid[i][j]*
                                       grid[i][j+1]*
                                       grid[i][j+2]*
                                       grid[i][j+3], max);
                    
                    if (i+3<=19 && j+3<=19)
                        max = Math.Max(grid[i][j] *
                                       grid[i+1][j + 1] *
                                       grid[i+2][j + 2] *
                                       grid[i+3][j + 3], max);
       
                    if (i - 3 >= 0 && j + 3 <= 19)
                        max = Math.Max(grid[i][j] *
                                       grid[i - 1][j + 1] *
                                       grid[i - 2][j + 2] *
                                       grid[i - 3][j + 3], max);
                }
            }

            Console.WriteLine("max is " + max);
            Console.ReadLine();
        }
    }
}