[MWIP] Sudoku solver

local args = { ... }
split = function( str )
local t = { }
for i = 1,str:len( ) do
  t[i] = str:sub( i, i )
end
return t
end
puzzle = {
{5,0,4,3,8,0,0,0,0};
{0,9,0,5,0,0,2,0,0};
{1,0,0,0,6,4,8,0,0};
{0,0,5,1,9,0,0,0,7};
{0,0,6,0,0,0,9,0,0};
{3,0,0,0,7,6,4,0,0};
{0,0,2,7,4,0,0,0,1};
{0,0,1,0,0,9,0,2,0};
{0,0,0,0,2,1,3,0,9};
}
if args[2] then
k = fs.open( args[2], "r" )
local con = { }
for i = 1,9 do
  con[i] = k.readLine( )
end
k.close( )
for i = 1,9 do
  print( con[i] )
  con[i] = split( con[i], "" )
  print( "here" )
  for k = 1,9 do
   con[i][k] = tonumber( con[i][k] ) or 0
  end
end
puzzle = con
end
term.clear( )
local correctpuzzle = {
{8,3,2,6,7,5,1,4,9};
{0,4,9,1,3,2,8,5,6};
{5,6,1,4,9,8,3,2,7};
{4,1,5,9,8,7,2,6,3};
{9,2,6,3,5,1,4,7,8};
{3,8,7,2,6,4,5,9,1};
{2,5,3,7,1,6,9,8,4};
{6,9,4,8,2,3,7,1,5};
{1,7,8,5,4,9,6,3,2};
}

local function checkBox( n )
if n < 1 or n > 9 then
  return nil
end
local x = 0
local y = 1
while n >= 4 do
  y = y+1
  n = n-3
end
x = x+n
local n = { }
for i = x*3-2, x*3 do
  for k = y*3-2, y*3 do
   n[puzzle[k][i]] = true
  end
end
for i = 1,9 do
  if not n[i] or n[i] ~= true then
   return false
  end
end
return true
end
local function checkColumn( n )
local num = { }
for i = 1,9 do
  num[puzzle[i][n]] = true
end
for i = 1,9 do
  if not num[i] or num[i] ~= true then
   return false
  end
end
return true
end
local function checkRow( n )
local num = { }
for i = 1,9 do
  num[puzzle[n][i]] = true
end
for i = 1,9 do
  if not num[i] or num[i] ~= true then
   return false
  end
end
return true
end
local function getPuzzle( )
local x = 1
local y = 1
while true do
  for i = 1,9 do
   for k = 1,9 do
	if i == y and x == k then
	 term.setBackgroundColour( colours.blue )
	else
	 term.setBackgroundColour( colours.lightBlue )
	end
	term.setCursorPos( k, i )
	term.write( tostring( puzzle[i][k] ):sub( 1, 1 ) )
   end
  end
  term.setCursorPos( 1, 10 )
  ev = { os.pullEvent( ) }
  if ev[1] == "key" then
   if ev[2] == keys.up and y > 1 then
	y = y - 1
   elseif ev[2] == keys.down and y < 9 then
	y = y + 1
   elseif ev[2] == keys.left and x > 1 then
	x = x - 1
   elseif ev[2] == keys.right and x < 9 then
	x = x + 1
   elseif ev[2] == keys.backspace then
	return false
   elseif ev[2] == keys.enter then
	return true
   end
  elseif ev[1] == "char" then
   puzzle[y][x] = tonumber( ev[2] ) or 0
  end
end
end
local function checkPuzzle( )
local message = "Failed"
for i = 1,9 do
  local f = checkRow( i )
  local s = checkColumn( i )
  local t = checkBox( i )
  if not f or not s or not t then
   if not f then
	message = message.."; R"..i
   end
   if not s then
	message = message.."; C"..i
   end
   if not t then
	message = message.."; B"..i
   end
   failed = true
  end
end
return message == "Failed" and "Fine" or message
end
local function getNumbers( ty, n, t )
local num = { }
if ty == "row" then
  for i = 1,9 do
   table.insert( num, t[n][i].n )
  end
elseif ty == "column" then
  for i = 1,9 do
   table.insert( num, t[i][n].n )
  end
elseif ty == "box" then
  local x = 0
  local y = 1
  while n >= 4 do
   y = y+1
   n = n-3
  end
  x = x+n
  local n = { }
  for i = x*3-2, x*3 do
   for k = y*3-2, y*3 do
	table.insert( num, t[k][i].n )
   end
  end
end
return num
end
local function solve( t, try )
local backupofpuzzle = { unpack( t ) }
if try > 1600 then
  return "unable to solve"
end
if math.floor( try/400 ) == try/400 then
  print( "This is taking a while" )
  sleep( 0.1 )
end
--converts it into a new format
for i = 1,9 do
  for k = 1,9 do
   t[i][k] = { n = t[i][k], pos = { } }
   for z = 1,9 do
	t[i][k].pos[z] = true
   end
  end
end
--removes incorrect possibilities
for i = 1,9 do
  --box checking
  local ns = getNumbers( "box", i, t )
  local n = i
  local x = 0
  local y = 1
  while n >= 4 do
   y = y+1
   n = n-3
  end
  x = x+n
  for m = 1,#ns do
   for y = y*3-2, y*3 do
	for x = x*3-2, x*3 do
	 if t[y][x].n == 0 then
	  t[y][x].pos[ns[m]] = false
	 end
	end
   end
  end
  --row checking
  local ns = getNumbers( "row", i, t )
  for m = 1,#ns do
   for x = 1,9 do
	if t[i][x].n == 0 then
	 t[i][x].pos[ns[m]] = false
	end
   end
  end
  --column checking
  local ns = getNumbers( "column", i, t )
  for m = 1,#ns do
   for x = 1,9 do
	if t[x][i].n == 0 then
	 t[x][i].pos[ns[m]] = false
	end
   end
  end
end
--updates the numbers ( if there is only one possibility then it has to be that... )
for i = 1,9 do
  for k = 1,9 do
   local correct = 0
   for z = 1,9 do
	if t[i][k].pos[z] == true then
	 correct = correct+1
	end
   end
   if correct == 1 then
	for z = 1,9 do
	 if t[i][k].pos[z] and t[i][k].n == 0 then
	  t[i][k].n = z
	 end
	end
   end
  end
end
--checks to see if it has completed the puzzle
local solved = true
for i = 1,9 do
  for k = 1,9 do
   if t[k][i].n == 0 then
	solved = false
   end
  end
end
--if it isn't solved then try again and
if not solved then
  --converts it back into just numbers
  for i = 1,9 do
   for k = 1,9 do
	t[i][k] = t[i][k].n
   end
  end
  if t == backupofpuzzle then
   for i = 1,9 do
	for k = 1,9 do
	 t[i][k] = { n = t[i][k] }
	end
   end
  else
   return solve( t, try+1 )
  end
end
--makes the rows of numbers into a string
local line = { }
for i = 1,9 do
  line[i] = ""
  for k = 1,9 do
   line[i] = line[i]..tostring( t[i][k].n )
  end
  line[i] = line[i].."\n"
end
return unpack( line )
end
if not getPuzzle( ) then
term.setBackgroundColour( colours.black )
term.setTextColour( colours.yellow )
print( "You Quitted" )
return
end
local failed = false
local message = "Failed"
if args[1] == "check" then
if checkPuzzle( puzzle ) ~= "Fine" then
  term.setBackgroundColour( colours.black )
  term.setTextColour( colours.red )
  print( checkPuzzle( puzzle ) )
  return
end
term.setBackgroundColour( colours.black )
term.setTextColour( colours.lime )
print( "It Works!" )
elseif args[1] == "solve" then
term.setBackgroundColour( colours.green )
print( solve( puzzle, 1 ) )
end