Validate Sudoku Board Algorithm

gistfile1.js

define([], function() {

  module("Sudoku");

  /*
  Write a function that takes a 9x9 array of integers and returns true if the following constraints are met:
  1. Each row must contain the numbers 1 to 9.
  2. Each column must contain the numbers 1 to 9.
  3. Each 3 x 3 local square must contain the numbers 1 to 9

  http://upload.wikimedia.org/wikipedia/commons/3/31/Sudoku-by-L2G-20050714_solution.svg
  */

  var good = [
    [5,3,4,6,7,8,9,1,2], //1
    [6,7,2,1,9,5,3,4,8], //2
    [1,9,8,3,4,2,5,6,7], //3
    [8,5,9,7,6,1,4,2,3], //4
    [4,2,6,8,5,3,7,9,1], //5
    [7,1,3,9,2,4,8,5,6], //6
    [9,6,1,5,3,7,2,8,4], //7
    [2,8,7,4,1,9,6,3,5], //8
    [3,4,5,2,8,6,1,7,9], //9
  ];

  var badRows = [
    [5,3,4,6,7,8,9,1,2], //1
    [6,7,2,1,9,5,3,4,8], //2
    [1,9,8,3,4,2,5,6,7], //3
    [8,5,9,7,6,1,4,2,3], //4
    [4,2,6,8,5,3,7,9,1], //5
    [7,1,3,9,2,4,8,5,6], //6
    [9,6,1,5,3,7,2,8,4], //7
    [2,8,7,4,1,9,6,3,5], //8
    [3,4,5,2,8,6,1,8,9], //9 variant last row repeats 8 twice
  ];

  var badColumns = [
    [5,3,4,6,7,8,9,1,2], //1
    [6,7,2,1,9,5,3,4,8], //2
    [1,9,8,3,4,2,5,6,7], //3
    [8,5,9,7,6,1,4,2,3], //4
    [4,2,6,8,5,3,7,9,1], //5
    [7,1,3,9,2,4,8,5,6], //6
    [9,6,1,5,3,7,2,8,4], //7 variant
    [2,8,7,4,1,9,6,3,4], //8 variant - last column repeats 4 twice
    [3,4,5,2,8,6,1,7,9], //9
  ];

  function validateGroup(group) {
    var validNumbers = [1,2,3,4,5,6,7,8,9], currentNum, idx;
    for (var i = 0; i < group.length; i++) {
      currentNum = group[i];
      idx = validNumbers.indexOf(currentNum);
      validNumbers[idx] = -1;
      if (idx == -1) return false
    }
    return true;
  }

  function validateRows(board) {
    for (var i = 0; i < board.length; i++) {
      if (!validateGroup(board[i])) return false;
    }
    return true;
  }

  function validateColumns(board) {
    var colNums = [];
    var idx = 0;
    var currentRow;
    while (idx < board.length) {
      for (var i = 0; i < board.length; i++) {
        currentRow = board[i];
        colNums.push(currentRow[idx]);
      }
      if (!validateGroup(colNums)) return false;
      colNums = [];
      idx++;
    }
    return true;
  }

  function validateBoard(board) {
    return validateRows(board) && validateColumns(board);
  }

  test("validate group of numbers (e.,g, a row, column or 3x3 square)", function() {
    var goodGroup = [1,2,3,4,5,6,7,8,9];
    var badGroup  = [2,2,3,4,5,6,7,8,9];

    equal(validateGroup(goodGroup), true);
    equal(validateGroup(badGroup), false);
  });

  test("validate many rows", function() {
    equal(validateRows(good), true);
    equal(validateRows(badRows), false);
  });

  test("validate columns", function() {
    equal(validateColumns(good), true);
    equal(validateColumns(badColumns), false);
  });

  test("validate board", function() {
    equal(validateBoard(good), true);
    equal(validateBoard(badRows), false);
    equal(validateBoard(badColumns), false);
  });

  // Note: I'm still looking into how to make a bad 3x3 square AND have 
  // valid rows and columns at the same time. If it turns out to be possible
  // I will update the solution. 
});