How to Use the Sudoku Module in Ruby to Solve Puzzles?

[sean1234]

I wrote the below code in a text editor, saved it as foo.rb Now I assume to run it, I simply go into the terminal and enter ruby foo.rb, yet nothing happens.

module Sudoku

class Puzzle
ASCII = ".123456789"
BIN = "\000\001\002\003\004\005\006\007\010\011"
def initialize(lines)
if (lines.respond_to? :join)
s = lines.join
else
s = lines.dup
end
s.gsub!(/\s/, "") # /\s/ is a Regexp that matches any whitespace

raise Invalid, "Grid is the wrong size" unless s.size == 81
if i = s.index(/[^123456789\.]/)
raise Invalid, "Illegal character #{s[i,1]} in puzzle"
end
s.tr!(ASCII, BIN)
@grid = s.unpack('c*')

raise Invalid, "Initial puzzle has duplicates" if has_duplicates?
end
def to_s
(0..8).collect{|r| @grid[r*9,9].pack('c9')}.join("\n").tr(BIN,ASCII)
end
def dup
copy = super
@grid = @grid.dup
copy
end
def [](row, col)
@grid[row*9 + col]
end
def []=(row, col, newvalue)
unless (0..9).include? newvalue
raise Invalid, "illegal cell value"
end
@grid[row*9 + col] = newline
end
BoxOfIndex = [
0,0,0,1,1,1,2,2,2,0,0,0,1,1,1,2,2,2,0,0,0,1,1,1,2,2,2,
3,3,3,4,4,4,5,5,5,3,3,3,4,4,4,5,5,5,3,3,3,4,4,4,5,5,5,
6,6,6,7,7,7,8,8,8,6,6,6,7,7,7,8,8,8,6,6,6,7,7,7,8,8,8
].freeze
def each_unknown
0.upto 8 do |row|
0.upto 8 do |col|
index = row*9+col
next if @grid[index] !=0
box = BoxofIndex[index]
yield row, col, box
end
end
end
def has_duplicates?
0.upto(8) {|row| return true if rowdigits(row).uniq! }
0.upto(8) {|col| return true if coldigits(col).uniq! }
0.upto(8) {|box| return true if boxdigits(box).uniq! }
false
end
AllDigits = [1,2,3,4,5,6,7,8,9].freeze
def possible(row, col, box)
AllDigits - (rowdigits(row) + coldigits(col) + boxdigits(box))
end
private
def rowdigits(row)
@grid[row*9,9] - [0]
end
def coldigits(col)
result = []
col.step(80, 9) {|i|
v = @grid
result << v if (v != 0)
}
result
end
BoxToIndex = [0, 3, 6, 27, 30, 33, 54, 57, 60].freeze
def boxdigits(b)
i = BoxToIndex
[
@grid, @grid[i+1], @grid[i+2],
@grid[i+9], @grid[i+10], @grid[i+11],
@grid[i+18], @grid[i+19], @grid[i+20]
] - [0]
end
end
class Invalid < StandardError
end
class Impossible < StandardError
end
def Sudoku.scan(puzzle)
unchanged = false
until unchanged
unchanged = true
rmin,cmin,pmin = nil
min = 10
puzzle.each_unknown do |row, col, box|
case p.size
when 0
raise Impossible
when 1
puzzle[row,col] = p[0]
unchanged = false
else
if unchanged && p.size < min
min = p.size
rmin, cmin, pmin = row, col, p
end
end
end
end
return rmin, cmin, pmin
end
def Sudoku.solve(puzzle)
puzzle = puzzle.dup
r,c,p = scan(puzzle)
return puzzle if r == nil
p.each do |guess|
puzzle[r,c] = guess

begin
return solve(puzzle)
rescue Impossible
next
end
end
raise Impossible
end
end

 

[dwahler]

Although you didn't make this clear, that code is from Example 1-1 of "The Ruby Programming Language" by David Flanagan and Yukihiro Matsumoto. Did you try reading the very first comment in the example?

 

[sean1234]

I guess that was a bit unclear for me. It says that it is a "module to solve Sudoku puzzles." I am not really certain what exactly that is.

 

[dwahler]

I was referring to this:

# Use this module to solve Sudoku puzzles with code like this:
#
#  require 'sudoku'
#  puts Sudoku.solve(Sudoku::Puzzle.new(ARGF.readlines))

Put that in a new file called "sudoku_solver.rb" or something and run it. You'll need to supply the input filename on the command line.