Solving Every Sudoku Puzzle (2006) | Hacker News Reader

Solving Every Sudoku Puzzle (2006)

norvig.com

73 pointsdjoldman26 comments

I've seen this article every now and then, and it's always fun to read. Something jumped out at me this time, though:

> As computer security expert Ben Laurie has stated, Sudoku is "a denial of service attack on human intellect". Several people I know (including my wife) were infected by the virus, and I thought maybe this would demonstrate that they didn't need to spend any more time on Sudoku.

Ah, yes... remember the halcyon days of 2006, when something as benign as Sudoku was considered to be a "denial of service attack on human intellect"?

It was a denial of service attack, not in the sense of soaking up my brain cells solving puzzles, but in causing me to devise and program my own solver. (In Java, text console only.) Once I wrote a solver, I felt as if I had solved all puzzles.

Then I got interested in devising puzzles with multiple solutions. Not too difficult. But making a few puzzles with two solutions was fun.

Experiment_203(

   " 1 . . | 2 . 8 | . . 9 "+
   " . 8 . | . . . | . 3 . "+
   " . . 7 | . 1 . | 2 . . "+
   //------+-------+--------
   " 4 . . | 1 2 3 | . . 6 "+
   " . . 2 | 4 5 6 | 9 . . "+
   " 6 . . | 7 8 9 | . . 4 "+
   //------+-------+--------
   " . . 6 | . 4 . | 8 . . "+
   " . 2 . | . . . | . 7 . "+
   " 9 . . | 8 . 2 | . . 1 "
  ),

// Solution #1. Found in 0 days 00:00:00.004.

// 245 boards examined so far.

   1 6 5 | 2 3 8 | 7 4 9
   2 8 4 | 6 9 7 | 1 3 5
   3 9 7 | 5 1 4 | 2 6 8
   ------+-------+------
   4 7 9 | 1 2 3 | 5 8 6
   8 3 2 | 4 5 6 | 9 1 7
   6 5 1 | 7 8 9 | 3 2 4
   ------+-------+------
   7 1 6 | 3 4 5 | 8 9 2
   5 2 8 | 9 6 1 | 4 7 3
   9 4 3 | 8 7 2 | 6 5 1

// Solution #2. Found in 0 days 00:00:00.001.

// 287 boards examined so far.

   1 6 5 | 2 3 8 | 7 4 9
   2 8 4 | 9 6 7 | 1 3 5  // <-- 9 6 7 instead of 6 9 7
   3 9 7 | 5 1 4 | 2 6 8
   ------+-------+------
   4 7 9 | 1 2 3 | 5 8 6
   8 3 2 | 4 5 6 | 9 1 7
   6 5 1 | 7 8 9 | 3 2 4
   ------+-------+------
   7 1 6 | 3 4 5 | 8 9 2
   5 2 8 | 6 9 1 | 4 7 3  // <-- 6 9 1 instead of 9 6 1
   9 4 3 | 8 7 2 | 6 5 1


   2 total solutions found.
   304 total boards examined.
   Total time 0 days 00:00:00.041.

Then I got to looking at difficult puzzles on the web. Apparently AI escargot is the world's most difficult. (And the site http://www.aisudoku.com/index_en.html says I can't publish the board). So I'll only publish the stats of applying my solver to it.

  Solution #1.  Found in 0 days 00:00:00.029.
  3,906 boards examined so far.

  1 total solutions found.
  7,832 total boards examined.
  Total time 0 days 00:00:00.085.

In that case, I have important news to tell you about! OpenAI has come out with am AI web browser! What is an AI web browser good for? I don't really know, but what you _can_ do, is log into hacker news with it, point it at your hacker news comment history, tell it to look at /newcomments page for stuff you'd want to comment on, and it'll shitpost for you!

What a wonderful time saver! Now you can get back to the important work of doing the dishes and folding laundry, and don't feel the need to personally participate in the denial of service attack on human intellect going on here.

Writing a sudoku solver/generator immediately and completely cured me of my crippling Sudoku addiction. I've been playing sudoku since I was probably 13, but after writing a solver I just can't muster up any interest to finish solving a puzzle. Not in a "my program could do this for me" sense, but more along the lines of "I've solved this and every other problem, now it's boring"

> As computer security expert Ben Laurie has stated, Sudoku is "a denial of service attack on human intellect". […] I thought maybe this would demonstrate that [my wife doesn’t] need to spend any more time on Sudoku.

The same could be said about every logic puzzle, or other types of puzzles.

People don't do them so actually solve any sort of new problem, or achieve some sort of productivity.

The same reason people don’t jog to get from point A to point B, or to learn how to get around more quickly.

Logic puzzles are exercising parts of our brain that don’t get exercised regularly.

Feels like the "demonstrated it's no longer necessary to solve sudokus" statement may have been a joke :)

Probably a joke... nevertheless I had the same reaction ! It exercises your deduction, binary thinking, also stochastic vs systematic methodology (first look around randomly find the most obvious before going number by number). Getting to discover all the tricks and reasoning in various "dimensions" is very satisfactory as well. But above all sudokuing puts you in a sort of meditative state : focusing your mind on this micro deductive world gets rid of all the noise and can be very relaxing between 2 pomodoros :)

Most logic puzzles such as the software pack made from SGT (or under the paper puzzle booklets, same concept but with pens and paper) are trivially solvable with computers and often STEM people will get bored with them fast. Solve it once, solve it for all.

If any, the challenge and fun would come by solving them with an algorithm under its favourite programming language.

Also, lateral thinking based riddles/puzzles are often more fun to solve, such as the crime related ones.

>denial of service attack on human intellect

Sounds like social media feeds these days

Crossword puzzles were the big fad puzzle in the 1920s.

I was a bit disappointed that he did not in fact solve all billions/trillons of possible sudoku puzzles.

You'd appreciate "Every 5x5 Nonogram": https://news.ycombinator.com/item?id=44140918

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