PyramidModel.cs

using System.Text;

namespace PyramidSolver
{
    public class PyramidModel
    {
        private readonly int[,] _data;

        public PyramidModel(PyramidModel pyramid)
        {
            _data = (int[,])pyramid._data.Clone();
            Rows = pyramid.Rows;
        }

        public PyramidModel(int[,] data)
        {
            _data = data;
            Rows = data.GetLength(0);
        }

        public PyramidModel(int rows)
        {
            _data = new int[rows, rows];
            Rows = rows;
        }

        public int this[int row, int col]
        {
            get => _data[row, col];
            set => _data[row, col] = value;
        }

        public int Rows { get; }

        /// <summary>
        /// Pretty print me
        /// </summary>
        public override string ToString()
        {
            var sb = new StringBuilder();

            for (var row = 0; row < Rows; row++)
            {
                sb.Append(new string(' ', 8 * row / 2));

                for (var col = 0; col < Rows - row; col++)
                {
                    sb.AppendFormat("[{0:00000}] ", _data[row, col]);
                }

                sb.AppendLine();
            }

            return sb.ToString();
        }
    }
}