SequenceInMatrix

using System;
using System.Collections.Generic;

class SequenceInMatrix
{
    static void Main()
    {
        List<List<string>> matrix = new List<List<string>>();

        string currentRowContents = Console.ReadLine();
        string[] currentRowTokens;
        for (int row = 0; !String.IsNullOrEmpty(currentRowContents); row++)
        {
            matrix.Add(new List<string>());
            currentRowTokens = currentRowContents.Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);
            for (int col = 0; col < currentRowTokens.Length; col++)
            {
                matrix[row].Add(currentRowTokens[col]);
            }

            currentRowContents = Console.ReadLine();
        }

        int currentLength = 1;
        int bestLength = int.MinValue;
        string bestValue = String.Empty;
        for (int row = 0; row < matrix.Count; row++)
        {
            for (int col = 0; col < matrix[row].Count; col++)
            {
                currentLength = CheckVertical(matrix, row, col, matrix[row][col]);
                if (currentLength > bestLength)
                {
                    bestLength = currentLength;
                    bestValue = matrix[row][col];
                }
                currentLength = CheckHorizontal(matrix, row, col, matrix[row][col]);
                if (currentLength > bestLength)
                {
                    bestLength = currentLength;
                    bestValue = matrix[row][col];
                }
                currentLength = CheckDiagonal(matrix, row, col, matrix[row][col]);
                if (currentLength > bestLength)
                {
                    bestLength = currentLength;
                    bestValue = matrix[row][col];
                }
            }
        }

        Console.Write(bestValue);
        for (int i = 1; i < bestLength; i++)
        {
            Console.Write(", {0}", bestValue);
        }
        Console.WriteLine();
    }

    private static int CheckDiagonal(List<List<string>> matrix, int row, int col, string currentValue)
    {
        int currentLength = 1;
        for (int i = row, j = col; i < matrix.Count && j < matrix[row].Count; i++, j++)
        {
            if (i + 1 < matrix.Count && j + 1 < matrix[i + 1].Count && matrix[i + 1][j + 1].Equals(currentValue))
            {
                currentLength++;
            }
            else
            {
                break;
            }
        }
        return currentLength;
    }

    private static int CheckHorizontal(List<List<string>> matrix, int row, int col, string currentValue)
    {
        int currentLength = 1;
        for (int i = col; i < matrix[row].Count; i++)
        {
            if (i + 1 < matrix[row].Count && matrix[row][i + 1].Equals(currentValue))
            {
                currentLength++;
            }
            else
            {
                break;
            }
        }
        return currentLength;
    }

    private static int CheckVertical(List<List<string>> matrix, int row, int col, string currentValue)
    {
        int currentLength = 1;
        for (int i = row; i < matrix.Count; i++)
        {
            if (i + 1 < matrix.Count && matrix[i + 1][col].Equals(currentValue))
            {
                currentLength++;
            }
            else
            {
                break;
            }
        }
        return currentLength;
    }
}