67

Explore Your Deductive Logic—Sudoku

67

STEP 22 Continued (Refreshcantbelist)

              If sbox(k, j) =​ cantbelist(i, j, kk) Then foundincantbelist =​ 1

              Next kk

              If foundincantbelist =​ 0 Then

              cantbelist(i, j, NextEmptyLocation(i, j)) =​ sbox(k, j)

            End If

          End If

        ‘ Next m

      End If

    Next k

    ‘*      check all cells in the 3x3 box this cell belongs to

       

      For k =​ 1 To 3

        n =​ Int((i -​ 1) /​ 3) * 3 +​ k

        For l =​ 1 To 3

          p =​ Int((j -​ 1) /​ 3) * 3 +​ l

          If (i =​ n And j =​ p) Then

            m =​ m ‘do nothing

          Else

 

          If sbox(n, p) <> ““ Then

            foundincantbelist =​ 0

            For kk =​ 1 To 9

            If sbox(n, p) =​ cantbelist(i, j, kk) Then foundincantbelist =​ 1

            Next kk

            If foundincantbelist =​ 0 Then

            cantbelist(i, j, NextEmptyLocation(i, j)) =​ sbox(n, p)

            End If

          End If

         

        End If

      Next l

    Next k

   

   

    Next j

    Next i

End Sub

3.9  CONCLUSION

Playing a Sudoku game is very entertaining. But to be able to solve it using your own

program is priceless. This chapter helps you to see the numerous patterns, which,

once coded into an algorithm, yield a surprising answer through the power of iter­

ation. This macro makes solving Sudoku much faster than a human being can!

There is a rather simple strategy that one can apply to Sudoku games—​fill in the

blanks with the nine possible digits (1–​9) and check if all the rows, columns, and 3 by

3 squares have unrepeated digits. But this algorithm takes very long to yield a result.