Class: Rudoku

Inherits:
Object
  • Object
show all
Defined in:
lib/rudoku.rb

Instance Method Summary collapse

Constructor Details

#initialize(sudoku) ⇒ Rudoku 



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# File 'lib/rudoku.rb', line 2

def initialize(sudoku)
  @n = sudoku.size
  @sqrt_n = Math.sqrt(@n).to_i
  raise "wrong sudoku size" unless @sqrt_n * @sqrt_n == @n

  @arr = sudoku.collect { |row|
    (0...@n).collect { |i|
      ((1..@n) === row[i]) ? [row[i]] : (1..@n).to_a
    }
  }

  @rfix = Array.new(@n) { [] }
  @cfix = Array.new(@n) { [] }
  @bfix = Array.new(@n) { [] }
  @n.times { |r| @n.times { |c| update_fix(r, c) } }

  [@rfix, @cfix, @bfix].each { |fix| fix.each { |x|
    unless x.size == x.uniq.size
      raise "non-unique numbers in row, col or box"
    end
  } }
end

Instance Method Details

#backtrack_solve ⇒ Object 



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# File 'lib/rudoku.rb', line 41

def backtrack_solve
  if (res = solve) == :unknown
    r, c = 0, 0
    @rfix.each_with_index { |rf, r|
      break if rf.size < @n
    }
    @arr[r].each_with_index { |x, c|
      break if x.size > 1
    }
    partial = to_a
    solutions = []
    @arr[r][c].each { |guess|
      partial[r][c] = guess
      rsolver = Rudoku.new(partial)
      case rsolver.backtrack_solve
      when :multiple_solutions
      initialize(rsolver.to_a)
      return :multiple_solutions
      when :solved
      solutions << rsolver
      end
    }
    if solutions.empty?
      return :impossible
    else
      initialize(solutions[0].to_a)
      return solutions.size > 1 ? :multiple_solutions : :solved
    end
  end
  res
end

#deduce ⇒ Object 



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# File 'lib/rudoku.rb', line 107

def deduce
  success = false
  [:col_each, :row_each, :box_each].each { |meth|
    @n.times { |i|
      u = uniqs_in(meth, i)
      unless u.empty?
        send(meth, i) { |x|
          if x.size > 1 && ((u2 = u & x).size == 1)
            success = true
            u2
          else
            nil
          end
        }
        return success if success
      end
    }
  }
  success
end

#finished? ⇒ Boolean 



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# File 'lib/rudoku.rb', line 86

def finished?
  @arr.each { |row| row.each { |x| return false if x.size > 1 } }
  true
end

#reduce ⇒ Object 



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# File 'lib/rudoku.rb', line 91

def reduce
  success = false
  @n.times { |r| @n.times { |c|
    if (sz = @arr[r][c].size) > 1
      @arr[r][c] = @arr[r][c] -
      (@rfix[r] | @cfix[c] | @bfix[rc2box(r, c)])
      raise "impossible to solve" if @arr[r][c].empty?
      if @arr[r][c].size < sz
        success = true
        update_fix(r, c)
      end
    end
  } }
  success
end

#solve ⇒ Object 



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# File 'lib/rudoku.rb', line 25

def solve
  begin
    until finished?
      progress = false
      while reduce
        progress = true
      end
      progress = true if deduce
      return :unknown unless progress
    end
    :solved
  rescue
    :impossible
  end
end

#to_a ⇒ Object 



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# File 'lib/rudoku.rb', line 73

def to_a
  @arr.collect { |row| row.collect { |x|
    (x.size == 1) ? x[0] : nil
  } }
end

#to_s ⇒ Object 



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# File 'lib/rudoku.rb', line 79

def to_s
  fw = @n.to_s.size
  to_a.collect { |row| row.collect { |x|
    (x ? x.to_s : "_").rjust(fw)
  }.join " " }.join "\n"
end