Sudoku Solver 9x9 [WIP]

board = {}
shell.run("delete console")
local h = fs.open("console","a")

function createEmptyBoard()
    for i = 1,9 do
        board[i] = {}
        for j = 1,9 do
            board[i][j] = {}
            board[i][j].num = 0
            board[i][j].exceptions = {}
            board[i][j].options = {}
        end
    end
end

function printBoard(xoff,yoff)
    xoff = xoff or 0
    yoff = yoff or 0
    for i=1,9 do
        for j=1,9 do
            term.setCursorPos(i + xoff,j + yoff)
            term.write(board[i][j].num)
        end
    end
end

--==Sudoku Functions==--
function findEmpty()
    for y = 1,9 do
        for x = 1,9 do
            if board[x][y].num == 0 then
                return true,x,y
            end
        end
    end
end

local function findQuadrant(x,y)
    quadrant = {}
    quadrant.num = 0
    quadrant.x = 0
    quadrant.y = 0
    if y <= 3 then

        if x<=3 then
            quadrant.num = 1
            quadrant.x = 1
            quadrant.y = 1
        elseif x<=6 then
            quadrant.num = 2
            quadrant.x = 4
            quadrant.y = 1
        elseif x<=9 then
            quadrant.num = 3
            quadrant.x = 7
            quadrant.y = 1
        end

    elseif y<=6 then

        if x<=3 then
            quadrant.num = 4
            quadrant.x = 1
            quadrant.y = 1
        elseif x<=6 then
            quadrant.num = 5
            quadrant.x = 4
            quadrant.y = 1
        elseif x<=9 then
            quadrant.num = 6
            quadrant.x = 7
            quadrant.y = 1
        end

    elseif y<=9 then

        if x<=3 then
            quadrant.num = 7
            quadrant.x = 1
            quadrant.y = 1
        elseif x<=6 then
            quadrant.num = 8
            quadrant.x = 4
            quadrant.y = 1
        elseif x<=9 then
            quadrant.num = 9
            quadrant.x = 7
            quadrant.y = 1
        end

    end
    return quadrant
end


local function organizeOptions(x,y)
    for i=1,9 do
        board[x][y].options[i] = i
    end
    for i = 1,9 do
        for _,k in pairs(board[x][y].exceptions) do
            if i == k then
                board[x][y].options[i] = 0
            end
        end
    end
end

function findOptions(x,y)
    for i = 1,9 do
        if board[i][y].num ~= 0 then
            table.insert(board[x][y].exceptions,board[i][y].num)
        end
        if board[x][i].num ~= 0 then
            table.insert(board[x][y].exceptions,board[x][i].num)
        end
    end
    quadrant = findQuadrant(x,y)
    for i = quadrant.x,quadrant.x+2 do
        for j = quadrant.y,quadrant.y+2 do
            if board[i][j].num ~= 0 then
                table.insert(board[x][y].exceptions,board[i][j].num)
            end
        end
    end
    organizeOptions(x,y)
end

function recursive()
    sleep(.000000001)
    log("recall")
    unsolved,x,y = findEmpty()
    if unsolved then
        findOptions(x,y)
        for _,v in pairs(board[x][y].options) do
            if v~= 0 then
                log("x: "..x)
                log("y: "..y)
                log("Decision: "..v)
                board[x][y].num = v
                recursive()
            end
        end
        board[x][y].num = 0
        log("backtrack")
    else
        term.clear()
        printBoard()
        print("FINISHED :D")
        error()
    end
end

--==Debug Functions==--

function fillRand()
    for i=1,4 do
        for j=1,4 do
            board[i][j].num = math.random(1,9)
        end
    end
end

function tab(t)
    for i,v in pairs(t) do
        if type(v) == "table" then
            tab(v)
        else
            print("i: ",i," v: ",v)
        end
    end
end

function log(s)
    if type(s) == "string" then
        h.writeLine(s)
        --print(s)
    else
        for i,v in pairs(s) do
            h.write("i: ")
            h.write(i)
            h.write(" v: ")
            h.writeLine(v)
            --print("i: ",i," v: ",v)
        end
    end
    h.flush()
end


createEmptyBoard()
term.clear()

board[1][1].num = 5
board[2][1].num = 3
board[5][1].num = 7

board[1][2].num = 6
board[4][2].num = 1
board[5][2].num = 9
board[6][2].num = 5

board[2][3].num = 9
board[3][3].num = 8
board[8][3].num = 6

board[1][4].num = 8
board[5][4].num = 6
board[9][4].num = 3

board[1][5].num = 4
board[4][5].num = 8
board[6][5].num = 3
board[9][5].num = 1

board[1][6].num = 7
board[5][6].num = 2
board[9][6].num = 6

board[2][7].num = 6
board[7][7].num = 2
board[8][7].num = 8

board[4][8].num = 4
board[5][8].num = 1
board[6][8].num = 9
board[9][8].num = 5

board[5][9].num = 8
board[8][9].num = 7
board[9][9].num = 9

printBoard(30,0)


--fillRand()
recursive()