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sudoku.rb
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#!/usr/bin/env ruby | |
class Solver | |
B = " " | |
attr_reader :sudoku_board | |
def initialize | |
@sudoku_board = [[B, 4, B, B, B, 5, B, 1, B], | |
[B, B, B, B, 1, B, 6, B, 9], | |
[6, B, 1, 9, 3, B, B, B, 4], | |
[5, B, 2, 6, 9, B, B, 7, B], | |
[B, 3, B, 7, B, 1, B, 9, B], | |
[B, 9, B, B, 4, 8, 1, B, 5], | |
[1, B, B, B, 7, 9, 8, B, 2], | |
[9, B, 3, B, 8, B, B, B, B], | |
[B, 7, B, 1, B, B, B, 4, B]] | |
end | |
def solve_init | |
return solve(0, 0, sudoku_board) | |
end | |
def solve(row, col, board) | |
# are we finished ? | |
if row == 9 | |
row = 0 | |
col += 1 | |
if col == 9 | |
return true | |
end | |
end | |
# are we on a spot that's filled already. skip. | |
if board[row][col] != B | |
return solve(row + 1, col, board) | |
end | |
# loop over remaining cells (here is where we recurse) | |
for val in 1..9 | |
# is the placement ok? | |
if ok_placement(row, col, board, val) | |
# set that cell and call solve on next space | |
board[row][col] = val | |
# if this solve is ok, return true | |
if solve(row + 1, col, board) | |
return true | |
end | |
end | |
end | |
board[row][col] = B | |
return false | |
# return false because loop ended with no solution | |
end | |
def ok_placement(row, col, board, attempt) | |
# check row | |
for check in 0..8 | |
if attempt == board[check][col].to_i | |
return false | |
end | |
end | |
# check vertical | |
for check in 0..8 | |
if attempt == board[row][check].to_i | |
return false | |
end | |
end | |
# check boxes | |
xBox = row / 3 * 3 # thanks to remainder chop off | |
yBox = col / 3 * 3 | |
for x in 0..2 | |
for y in 0..2 | |
if attempt == board[ (xBox + x) ][ (yBox + y) ].to_i | |
return false | |
end | |
end | |
end | |
return true | |
end | |
def print_board | |
i = j = 0 | |
9.times do | |
# draw horizontal line | |
if i == 0 | |
print "-" * 13 | |
puts "" | |
end | |
9.times do | |
# start box | |
if j == 0 | |
print "|" | |
end | |
print sudoku_board[i][j] | |
# put box after 3, 6 and 9th number | |
if j.modulo(3) == 2 | |
print "|" | |
end | |
j += 1 | |
end | |
puts "" | |
# draw remaining horizontal lines | |
if i.modulo(3) == 2 | |
print "-" * 13 | |
puts "" | |
end | |
j = 0 | |
i += 1 | |
end | |
end | |
end | |
s = Solver.new | |
puts "Before solving" | |
s.print_board | |
puts "Solving..." | |
solved = s.solve_init | |
puts "Finished!" | |
if solved | |
s.print_board | |
else | |
puts "No solution..." | |
end |
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