Sudoku Grader


2 years ago


Web App


2 years ago


Finally got round to starting this project. The idea is to emulate the various different approaches people take to solve the puzzle and then try all of them to determine the average time each takes to solve it (if at all). Seems that everyone has a different approach to the problem. Longer term I wonder whether it might be able to parse a solving algorithm from a free text description of an individuals method.


So far, I've set about making sure the 'sudoku' object has the means to address individual rows, columns and boxes as well as individual cells. I then added a couple of methods that I use to solve it and tested them against a couple of different puzzles. It seems to work, or at least it gets as far as I do with those techniques.

I played around with using a proxy for visualisation and it kind of worked. I just added a function that highlighted the cell whenever that cell object's value was read or changed (get or set). Problem is the animation runs asynchronously but the puzzle solving methods run synchronously so it didn't look right. In the end I changed the solving methods to generator functions and iterate over them with setInterval.


Enter digits in the grid; you can use arrow keys on keyboard or click / touch.

Hover over (or touch on mobile) any cell to view the digits it could be. This updates automatically whenever a cell changes.

Use 'Save' to store the current puzzle state so you can return to the beginning if you want.

Use a combination of different search methods to solve the puzzle. Or just click Solve.

Use 'Ultra' mode unless you want to wait all day! But 'Slow' is useful for working out what the different searches do.

Use the arrow keys to scroll backwards and forward digit by digit

  • Not Search - For every blank that has changed state, remove all the digits in that cells row, column and box from it's 'maybes' list. If only one remains, enter it.
  • Not Check - Additional method that checks all the affected cells whenever a value is entered to see if they can now be only one thing. Basically makes 'Not Search' redundant.
  • Box Search - For each box, create list of cells where each digit could go. If only one place, enter it. If only 2 places, and they are on the same row or column, update the rest of the group's maybes lists
  • Line Check - Additional check after box search, if digit can only be in 2 or 3 cells on the same row or column, then it can't be anywhere else on that line
  • Column Search - For each column, create list of cells where each digit could go. If only one place, enter it.
  • Row Search - For each row, create list of cells where each digit could go. If only one place, enter it.
  • Solve - Not, Box, Column and Row search until no blanks remain or maximum iterations reached. Now runs with visuals on thanks to async promises.
  • Tree Search - Triggered if 'Solve' fails, recursively tries all the possible values a cell could be and attempts to solve it. Can be used to solve a blanks grid.

  • Fix that chrome mobile bug - stupid keycodes
  • Clarify UI options
Bugs / Issues

Problem on Chrome on Android - for some reason they use the wrong keycodes on keyup event. Works fine on desktop chrome and mobile firefox.

Safari (iOS and desktop) - seems to be because they don't support the latest ES6 language features like Arrow functions. Will use Babel to transpile at some point.

  • Sudoku Solver (2 years ago)

    Making the most of my time off by making a sudoku solver. Plan is to dumb it down and use it as a difficulty rater by comparing the effectiveness of different techniques. For now it just solves puzzles..

  • Added visual feedback (2 years ago)

    Major upgrade: Added visualisation with adjustable speed setting (using generator functions and setInterval). Also improved mobile experience although still buggy on chrome. Added screenshots to the project page.

  • Solves Blank Grid (2 years ago)

    Refactored the tree search algorithm so that it now solves an empty grid. Previously it just simulated blanks that had 2 options now it runs recursively over all options of all blanks until it solves or determines that the puzzle is unsolvable. Pretty sweet.

  • Babelified to ES5 - Now works on Safari and older browsers (2 years ago)

    Added some tooling to transpile the source into ES5 so that it works on desktop and mobile safari. Although desktop solve methods are really slow, seems to be to do with the regenerator runtime. Also had to remove my use of proxies as it turns out there is no ES5 equivalent.


Connect on..

Or send me a nice old-fashioned..