sudoku.coffee

class window.Sudoku
  constructor: (board) ->
    @board = board

  solve: ->
    []

  column: (index) ->
    (cell for cell,cellIndex in @board when cellIndex % 9 == index)

  row: (index) ->
    @board.slice(index*9, index*9+9)

  box: (index) ->
    mod3 = index % 3
    i = (index-mod3)*9 + mod3*3
    _([0..2]).chain().map((row) -> @board.slice(i+row*9,i+row*9+3)).flatten().value()

  isValid: (bunch) ->
    _(bunch).intersection([1..9]).length == 9

sudoku_spec.coffee

describe "Sudoku", ->
  n=null
  Given -> @board = [
     7,9,n, n,n,n, 3,n,n,
     n,n,n, n,n,6, 9,n,n,
     8,n,n, n,3,n, n,7,6,

     n,n,n, n,n,5, n,n,2,
     n,n,5, 4,1,8, 7,n,n,
     4,n,n, 7,n,n, n,n,n,

     6,1,n, n,9,n, n,n,8,
     n,n,2, 3,n,n, n,n,n,
     n,n,9, 3,n,n, n,n,n
    ]
  Given -> @sudoku = new Sudoku(@board)

  xdescribe "#solve", ->
    When -> @solution = @sudoku.solve()
    Then -> expect(@solution).toEqual [
       7,9,6, 8,5,4, 3,2,1,
       2,4,3, 1,7,6, 9,8,5,
       8,5,1, 2,3,9, 4,7,6,

       1,3,7, 9,6,5, 8,4,2,
       9,2,5, 4,1,8, 7,6,3,
       4,6,8, 7,2,3, 5,1,9,

       6,1,4, 5,9,7, 2,3,8,
       5,8,2, 3,4,1, 6,9,7,
       3,7,9, 6,8,2, 1,5,4
      ]

  describe "#column", ->
    context "first row", ->
      When -> @result = @sudoku.column(0)
      Then -> expect(@result).toEqual [7,n,8,n,n,4,6,n,n]

    context "fifth row", ->
      When -> @result = @sudoku.column(4)
      Then -> expect(@result).toEqual [n,n,3,n,1,n,9,n,n]

  describe "#row", ->
    context "third row", ->
      When -> @result = @sudoku.row(2)
      Then -> expect(@result).toEqual [8,n,n,n,3,n,n,7,6]

    context "seventh row", ->
      When -> @result = @sudoku.row(6)
      Then -> expect(@result).toEqual [6,1,n,n,9,n,n,n,8]

  describe "#box", ->
    context "the center box", ->
      When -> @result = @sudoku.box(4)
      Then -> expect(@result).toEqual [n,n,5,
                                       4,1,8,
                                       7,n,n]

    context "the bottom-right box", ->
      When -> @result = @sudoku.box(8)
      Then -> expect(@result).toEqual [n,n,8,
                                       n,n,n,
                                       n,n,n]

  describe "#isValid", ->
    context "missing 5", ->
      When -> @result = @sudoku.isValid([1,3,7, 9,6,null, 8,4,2,])
      Then -> expect(@result).toEqual false

    context "two 2's", ->
      When -> @result = @sudoku.isValid([1,2,7, 9,6,5, 8,4,2,])
      Then -> expect(@result).toEqual false

    context "all of 1 through 9", ->
      When -> @result = @sudoku.isValid([1,3,7, 9,6,5, 8,4,2])
      Then -> expect(@result).toEqual true