Fwd: Sudoku


#1

Begin forwarded message:

From: NILSSON Christer removed_email_address@domain.invalid
Date: December 30, 2005 4:09:59 AM CST
To: James Edward G. II removed_email_address@domain.invalid
Subject: Re: Ruby Q. Suggestion
Reply-To: NILSSON Christer removed_email_address@domain.invalid

Hello James!

[snip]

I found a short solution for Sudoku. It was originally written by
Kevin Greer in JavaScript, but Ruby makes it look even nicer. I
haven’t seen the use of this data structure in Sudoku before.

[snip]


#2

Greetings,

While it may be true that the Sudoku program below looks nicer in
Ruby than JavaScript, I don’t find it very readable. Sure, it’s
concise, but that doesn’t help me understand it. The variable names
are horrible. As I learn Ruby, I’m seeing more and more of this poor
naming, favoring conciseness so much over clarity that some code
samples are outright frustrating to read for this “nuby.” I hope that
I’m just stumbling on some bad examples and not the norm. I hope that
the more Ruby code I read, the more I’ll find a pragmatic compromise
between conciseness and clarity.

Regards,
Craig


#3

Craig D. wrote:

The variable names are horrible.

Yes, you are correct. This is puzzle code, not production code. So part
of this is being puzzled! :slight_smile:

Joke aside, I considered using better variable names instead of a,b,c
and d, but did not find good candidates. Let me explain:

a, c = row.divmod(3) # row in 0…8
b, d = col.divmod(3) # col in 0…8

Maybe a=rowMajor, c=rowMinor, b=colMajor and d=colMinor would be more
helpful.

Fixing rowMajor and colMajor gives a 3x3 block:
s[rowMajor][colMajor][x][y], x in 0…2, y in 0…2
Fixing rowMajor and rowMinor gives a row
s[rowMajor][x][rowMinor][y]
Fixing colMajor and colMinor gives a column
s[x][colMajor][y][colMinor]

I hope this clarifies the code.

Christer


#4

2005/12/30, Craig D. removed_email_address@domain.invalid:

While it may be true that the Sudoku program below looks nicer in
Ruby than JavaScript, I don’t find it very readable. Sure, it’s
concise, but that doesn’t help me understand it.

i wouldn’t call it concise, it simply doesn’t work… probably an error
in
porting to Ruby…
the idea of simply going through every number and checking possibility
is
nice, but not enough, because a lot of numbers might fit, though only
one
will get you the proper solution.


#5

Link to the original Javascript code by Kevin Greer:

http://www.peerbox.com:8668/space/start/2005-12-5/1#Soduko_Solver_in_JavaScript

Christer


#6

Dirk M. wrote:

i wouldn’t call it concise, it simply doesn’t work… probably an error
in porting to Ruby…

It works. This is the complete code.
Christer

Author: Kevin Greer (JavaScript), Date: Dec 25, 2005 – Copyright

2005, All Rights Reserved

Rewritten in Ruby by Christer N. 2005-12-29

class Sudoku

def initialize s
@s=s
end

def display
for a in 0…2
for b in 0…2
for c in 0…2
for d in 0…2
print " " + @s[a][b][c][d].to_s
end
print " |" if c<2
end
print “\n”
end
print “-------±------±------\n” if a<2
end
end

def solve a, b, c, d
return true if a==3
return solve(a+1, 0, c, d) if b==3
return solve(a, b+1, 0, d) if c==3
return solve(a, b, c+1, 0) if d==3
return solve(a, b, c, d+1) if @s[a][b][c][d]!=0

for digit in 1..9
  if not occupied?(a, b, c, d, digit) then
    @s[a][b][c][d] = digit
    return true if solve(a, b, c, d+1)
    @s[a][b][c][d] = 0
  end
end
false

end

def occupied? a, b, c, d, digit
for x in 0…2
for y in 0…2
return true if @s[a][b][x][y]==digit # block
return true if @s[a][x][c][y]==digit # row
return true if @s[x][b][y][d]==digit # column
end
end
false
end
end

s =
[[[[0,0,0],[0,7,1],[0,0,5]],
[[5,0,0],[0,6,9],[0,7,1]],
[[0,7,1],[8,5,3],[4,2,0]]],
[[[0,1,0],[0,0,2],[0,0,0]],
[[7,8,0],[1,5,4],[0,9,2]],
[[0,4,0],[3,6,0],[1,8,0]]],
[[[0,6,4],[0,2,3],[0,5,0]],
[[9,0,5],[0,1,0],[0,0,0]],
[[7,0,0],[5,9,0],[0,0,0]]]]
sudoku = Sudoku.new(s)
sudoku.display
print “\nsolving…\n\n”
if sudoku.solve(0,0,0,0) then
sudoku.display
end

0 0 0 | 0 7 1 | 0 0 5
5 0 0 | 0 6 9 | 0 7 1
0 7 1 | 8 5 3 | 4 2 0
-------±------±------
0 1 0 | 0 0 2 | 0 0 0
7 8 0 | 1 5 4 | 0 9 2
0 4 0 | 3 6 0 | 1 8 0
-------±------±------
0 6 4 | 0 2 3 | 0 5 0
9 0 5 | 0 1 0 | 0 0 0
7 0 0 | 5 9 0 | 0 0 0

solving…

2 3 9 | 4 7 1 | 6 8 5
5 4 8 | 2 6 9 | 3 7 1
6 7 1 | 8 5 3 | 4 2 9
-------±------±------
5 1 6 | 8 9 2 | 3 4 7
7 8 3 | 1 5 4 | 6 9 2
9 4 2 | 3 6 7 | 1 8 5
-------±------±------
1 6 4 | 7 2 3 | 9 5 8
9 2 5 | 8 1 6 | 4 3 7
7 3 8 | 5 9 4 | 2 1 6

Program exited with code 0


#7

Correct link:

http://www.peerbox.com:8668/space/start/2005-12-25/1#Soduko_Solver_in_JavaScript

cheers


#8

Christer N. wrote:

2005, All Rights Reserved
for b in 0…2
end
@s[a][b][c][d] = digit
return true if @s[a][b][x][y]==digit # block
[[5,0,0],[0,6,9],[0,7,1]],
if sudoku.solve(0,0,0,0) then
0 4 0 | 3 6 0 | 1 8 0
-------±------±------
5 1 6 | 8 9 2 | 3 4 7
7 8 3 | 1 5 4 | 6 9 2
9 4 2 | 3 6 7 | 1 8 5
-------±------±------
1 6 4 | 7 2 3 | 9 5 8
9 2 5 | 8 1 6 | 4 3 7
7 3 8 | 5 9 4 | 2 1 6

Program exited with code 0

First Column has two 9’s !

cheers

Simon


#9

First Column has two 9’s !

and it leaves my tests with zero’s…
greetings, Dirk.


#10

First Column has two 9’s !
cheers
Simon

Excellent observation, Simon!

The error is in the display definition:

  •        print " " + @s[a][b][c][d].to_s
    
  •        print " " + @s[a][c][b][d].to_s
    

New output:

2 3 9 | 5 4 8 | 6 7 1
4 7 1 | 2 6 9 | 8 5 3
6 8 5 | 3 7 1 | 4 2 9
-------±------±------
5 1 6 | 7 8 3 | 9 4 2
8 9 2 | 1 5 4 | 3 6 7
3 4 7 | 6 9 2 | 1 8 5
-------±------±------
1 6 4 | 9 2 5 | 7 3 8
7 2 3 | 8 1 6 | 5 9 4
9 5 8 | 4 3 7 | 2 1 6

Sorry, I shouldn’t have opened that bottle of champagne yet!

Christer


#11

Dirk M. wrote:

and it leaves my tests with zero’s…
greetings, Dirk.

Would you mind sending me your input, Dirk?

Christer


#12

Christer N. removed_email_address@domain.invalid:

Would you mind sending me your input, Dirk?

it seems this was also a problem with the arrays,
i had entered the puzzle from left to right, i just found out it had to
be
done one block at the time…
anyway, sorry for the fuzz :wink:
greetings, Dirk.