X-Removal

namespace X_Removal
{
    using System;
    using System.Collections.Generic;

    class XRemoval
    {
        static void Main(string[] args)
        {
            List<string> textLines = new List<string>();
            List<bool[]> output = new List<bool[]>();
            string inputLine = Console.ReadLine();
            while (inputLine != "END")
            {
                textLines.Add(inputLine);
                output.Add(new bool[inputLine.Length]);

                inputLine = Console.ReadLine();
            }

            for (int row = 0; row < textLines.Count; row++)
            {
                for (int col = 0; col < textLines[row].Length; col++)
                {
                    if (col + 2 >= textLines[row].Length ||
                        row + 2 >= textLines.Count || col + 1 >= textLines[row + 1].Length ||
                        col + 2 >= textLines[row + 2].Length) continue;

                    RemoveXShape(textLines, row, col, output);
                }
            }

            PrintResults(textLines, output);
        }

        private static void RemoveXShape(List<string> matrix, int row, int col, List<bool[]> result)
        {
            char xshape = char.ToLower(matrix[row][col]);
            if (char.ToLower(matrix[row][col + 2]) != xshape ||
                char.ToLower(matrix[row + 1][col + 1]) != xshape ||
                char.ToLower(matrix[row + 2][col]) != xshape ||
                char.ToLower(matrix[row + 2][col + 2]) != xshape) return;

            result[row][col] = true;
            result[row][col + 2] = true;
            result[row + 1][col + 1] = true;
            result[row + 2][col] = true;
            result[row + 2][col + 2] = true;
        }

        private static void PrintResults(List<string> matrix, List<bool[]> result)
        {
            for (int row = 0; row < matrix.Count; row++)
            {
                for (int col = 0; col < matrix[row].Length; col++)
                {
                    if (result[row][col]) continue;

                    Console.Write(matrix[row][col]);
                }

                Console.WriteLine();
            }
        }
    }
}