Generate a random array in Javascript/jquery for Sudoku puzzle

Question

I want to fill the 9 x 9 grid from the array by taking care of following condition

1. A particular number should not be repeated across the same column.
2. A particular number should not be repeated across the same row.

When i execute the below mentioned code it fills all the 9 X 9 grid with random values without the above mentioned condition.How can I add those two condition before inserting values into my 9 X 9 Grid.

var sudoku_array = ['1','2','3','4','6','5','7','8','9'];

$('.smallbox input').each(function(index) {
    $(this).val(sudoku_array[Math.floor(Math.random()*sudoku_array.length)]);

});

My JSFIDDLE LINK

Answer 1

Generating and solving Sudokus is actually not as simple as other (wrong) answers might suggest, but it is not rocket science either. Instead of copying and pasting from Wikipedia I'd like to point you to this question.

However, since it is bad practice to just point to external links, I want to justify it by providing you at least with the intuition why naive approaches fail.

If you start generating a Sudoku board by filling some fields with random numbers (thereby taking into account your constraints), you obtain a partially filled board. Completing it is then equivalent to solving a Sudoku which is nothing else than completing a partially filled board by adhering to the Sudoku rules. If you ever tried it, you will know that this is not possible if you decide on the next number by chosing a valid number only with respect to the 3x3 box, the column and the row. For all but the simplest Sudokus there is some trial and error, so you need a form of backtracking.

I hope this helps.

Answer 2

To ensure that no number is repeated on a row, you might need a shuffling function. For columns, you'll just have to do it the hard way (checking previous solutions to see if a number exists on that column). I hope i am not confusing rows for columns, i tend to do it a lot.

It's similar to the eight queens problem in evolutionary computing. Backtracking, a pure random walk or an evolved solution would solve the problem.

This code will take a while, but it'll do the job.

You can the iterate through the returned two dimensional array, and fill the sudoku box. Holla if you need any help with that

Array.prototype.shuffle = function() {
  var arr = this.valueOf();
  var ret = [];
  while (ret.length < arr.length) {
    var x = arr[Math.floor(Number(Math.random() * arr.length))];
    if (!(ret.indexOf(x) >= 0)) ret.push(x);
  }
  return ret;
}

function getSudoku() {
  var sudoku = [];
  var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  sudoku.push(arr);
  for (var i = 1; i < 9; i++) {

    while (sudoku.length <= i) {
      var newarr = arr.shuffle();
      var b = false;
      for (var j = 0; j < arr.length; j++) {
        for (var k = 0; k < i; k++) {
          if (sudoku[k].indexOf(newarr[j]) == j) b = true;
        }

      }
      if (!b) {
        sudoku.push(newarr);
        document.body.innerHTML += `${newarr}<br/>`;
      }
    }
  }
  return sudoku;
}

getSudoku()