https://sugoku.onrender.com/

Go Challenge 8 solution for the month of November 2015.

*The API is hosted on a Render free tier instance. The server gets spun down with inactivity, expect a delay of 50 secs or more for the initial request. Then it's ⚡

Sudoku web app: solves, generates, grades, and validates sudoku puzzles.

The algorithm implements two solving functions:

1. QuickFill - Called so because it quickly checks horizontally, vertically and in the nine grid box for possible options. If only one possible solution remains, it adds the value to the square.

2. Guess - It fills an empty square with a possible, non-conflicting value. If the puzzle is solved (completely filled), it validates to see if it correct. If not, it goes back and fills the square with another possible value. It recursively fills in and backtracks until the puzzle is complete.

A very interesting finding was that implementing the QuickFill function before each guess did not improve the speed of the algorithm, in fact, it slowed it down. I was not expecting it. I was so surprised that I decided to keep the original name I had given the function without Quickfill: SlowSolve().

SlowSolve is the faster function and therefore the one used for the API.

go get github.com/bertoort/sugoku

• Go
• Gin
• Semantic UI
• jQuery
• Render
• Godep

Board - returns a puzzle board

https://sugoku.onrender.com/board

Arguments -

• Difficulty:
  • easy
  • medium
  • hard
  • random

Example:

https://sugoku.onrender.com/board?difficulty=easy

Solve - returns the solved puzzle, along with difficulty and status

https://sugoku.onrender.com/solve

Grade - returns the difficulty of the puzzle

https://sugoku.onrender.com/grade

Validate - returns the status of the puzzle

https://sugoku.onrender.com/validate

The request does not support content-type of application/json. It must be application/x-www-form-urlencoded

To help, here is a quick and dirty encoding functions for a board:

const encodeBoard = (board) => board.reduce((result, row, i) => result + `%5B${encodeURIComponent(row)}%5D${i === board.length -1 ? '' : '%2C'}`, '')

const encodeParams = (params) =>
  Object.keys(params)
  .map(key => key + '=' + `%5B${encodeBoard(params[key])}%5D`)
  .join('&');

Here is an example sending a board:

const data = {board:[[0,0,0,0,0,0,8,0,0],[0,0,4,0,0,8,0,0,9],[0,7,0,0,0,0,0,0,5],[0,1,0,0,7,5,0,0,8],[0,5,6,0,9,1,3,0,0],[7,8,0,0,0,0,0,0,0],[0,2,0,0,0,0,0,0,0],[0,0,0,9,3,0,0,1,0],[0,0,5,7,0,0,4,0,3]]}

fetch('https://sugoku.onrender.com/solve', {
  method: 'POST',
  body: encodeParams(data),
  headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
})
  .then(response => response.json())
  .then(response => console.log(response.solution))
  .catch(console.warn)

var data = {
  board: "[[0,0,1,0,0,0,0,0,0],
          [2,0,0,0,0,0,0,7,0],
          [0,7,0,0,0,0,0,0,0],
          [1,0,0,4,0,6,0,0,7],
          [0,0,0,0,0,0,0,0,0],
          [0,0,0,0,1,2,5,4,6],
          [3,0,2,7,6,0,9,8,0],
          [0,6,4,9,0,3,0,0,1],
          [9,8,0,5,2,1,0,6,0]]"
}
$.post('https://sugoku.onrender.com/solve', data)
  .done(function (response) {

    <% response = {
      difficulty: "hard",
      solution: Array[9],
      status: "solved"
    } &>

  });```

For more, check out the [api.js](https://github.com/bertoort/sugoku/blob/master/public/api.js) file