uqac-ia-sudoku-csp/uqac-ia-sudoku-csp/Solver/Constraints/BlockConstraint.cs

using System;
using uqac_ia_sudoku_csp.Interfaces;

namespace uqac_ia_sudoku_csp.Solver.Constraints
{
    public class BlockConstraint : IConstraint
    {
        public bool Check(Board board, int x, int y)
        {
            var bs = Math.Sqrt(board.Size);
            var sx = x / 3 * 3;
            var sy = y / 3 * 3;
            var cell = board.GetNumber(x, y).Value;
            for (var xx = sx; xx < sx + bs; ++xx)
            {
                for (var yy = sy; yy < sy + bs; ++yy)
                {
                    if (cell == board.GetNumber(xx, yy) && (xx != x || yy != y))
                    {
                        return false;
                    }
                }
            }
            return true;
        }
    }
}