boolean isBlockDiag(int y, int x, int yp, int xp) {
        int dy = yp-y;
        int dx  = xp-x;
        if(Math.abs(dy)==1 && Math.abs(dx)==1)
        {
          if(this.isValidCord(y+dy, x) && this.isValidCord(y, x+dx))
          {
              if(this.isBlocked(y+dy, x) && this.isBlocked(y, x+dx))
              return true;
          }
        }
        return false;
    }