PM of Singapore Shares His C++ Sudoku Solver Source Code

https://drive.google.com/folderview?id=0B2G2LjIu7WbdfjhaUmVzc1lCR2hUdk5fZllCOHdtbFItbU5qYzdqZGVxdmlnRkJyYVQ4VU0&usp=sharing&usp=sharing&urp=https://drive.google.com/folderview?id%3D0B2G2LjIu7W#list

by doppp • 11 years ago

209 150 11 years ago

drive.google.com

doppp• 11 years ago

I've put it on GitHub in case this is ever removed. :)

https://github.com/Doppp/LHL-Sudoku-Solver

onderkalaci• 11 years ago

Yeap, great idea :)

michael_h• 11 years ago

Code without a license on it is not public domain. In this instance, he probably won't care, but it's a bad habit to get into.

kenrick952• 11 years ago

Remarkable. He uses lots of bitwise operations in the application.

efaref• 11 years ago

He's using integers as sets of (small) integers,

    int Possibles = Block[BlockIndex] & Row[RowIndex] & Col[ColIndex];
    while (Possibles) {
        int valbit = Possibles & (-Possibles); // Lowest 1 bit in Possibles
        Possibles &= ~valbit;
        Entry[Square] = valbit;
        Block[BlockIndex] &= ~valbit;
        Row[RowIndex] &= ~valbit;
        Col[ColIndex] &= ~valbit;

is more generally:

    set<int> possibles = block[block_index].intersect(row[row_index]).intersect(col[col_index]);
    while (!possibles.is_empty())
    {
        int value = possibles.pop();
        entry[square] = value;
        block[block_index].remove(value);
        row[row_index].remove(value);
        col[col_index].remove(value);

nothrabannosir• 11 years ago

I like this one a lot:

    Entry[Square] = BLANK; // Could be moved out of the loop

Maybe I'm reading too much into it, but this type of thinking makes me smile. The guilty perfectionism, "this can be improved."

Were I from Singapore, I'd be happy to see it in the person in charge of my country.

casion• 11 years ago

While I find the code to be interesting, I wouldn't exactly claim to want this person as my PM.

Great, he used to program and displayed a handful of positive character qualities in doing so. A lot more than that is required to be an effective leader of a country.

delinka2• 11 years ago

Certainly a lot more is required. But this demonstrates that he's not some high-level politician that's completely out of touch with today's reality. It shows he's capable of logical thought. Two qualities I'd prioritize over all others in my leading politicians.

Bockit• 11 years ago

I think the distinction the grandparent made was they would be happy to see the trait in the leader of the country, not that seeing the trait makes a good leader.

dagw3• 11 years ago

I'd be happy to see it in the person in charge of my country.

Would you be equally happy to see Herman Cain as President of the US? He also has Masters in CS and spent the early parts of his career as a programmer.

personjerry2• 11 years ago

I think you're focusing too much on the particular detail. The idea of the comment as I understand it is that the code shows attention to detail which is a desirable trait in a leader.

steinnes• 11 years ago

You would be happy to have a person who mixes tabs and spaces as your PM? ... mixes tabs and spaces. Argh.

naz• 11 years ago

That's a pretty common style in C++. If he were a Ruby programmer and did that, then I'd be less happy.

personjerry2• 11 years ago

Ok I believe the phrasing of this comment makes its point a little unclear. Some people are saying how this demonstration doesn't guarantee that the president is a good one. This is true, but I believe the original comment here is merely saying that it is better to have a president WITH this characteristic than without.

coldtea3• 11 years ago

This is true, but I believe the original comment here is merely saying that it is better to have a president WITH this characteristic than without.

Or maybe there's no correlation at all? In the sense that NO, it's not better to have a presidnet with this characteristic thna without, it's equally likely that both the president with and without this can be a bad politician.

arianvanp2• 11 years ago

Please remember that Signapore has no free speech. I am kind of angry we're cirlclejerking about a PM whose a criminal according to my view http://en.wikipedia.org/wiki/Human_rights_in_Singapore

Can we please just ignore this dictator and be amazed about code of other people instead?

It just feels wrong.... I think freedom of speech is a very very important part of the hacker community. I think no sane person would want this person in charge of his country. Coder or not.

mikedmiked• 11 years ago

Controls on speech were necessary for Singapore to move from a third world country to a first world one in just 30 years

naithemilkman2• 11 years ago

Dictator? I don't think you know what that word means. Maybe you should come visit and see exactly how off the mark your comments are.

rplnt• 11 years ago

I notice this kind of behavior a lot. People praising someone for silly little things (even when the person does not deserve to be praised in general). One that comes to mind that gets this kind of response a lot would be the current pope.

fusiongyro• 11 years ago

Yes, let's ignore the programming aspect of this story so we can focus on the political aspect instead. That's what HN is for.

josai5• 11 years ago

I am sick of seeing "free speech" treated almost as religious dogma, as if it is axiomatically good. It's not - it's just a theory that unrestricted free speech will lead to a better society. Frankly, I don't think that is anywhere near proven yet (nor do I think even democracy has been "proven" to work long-term).

I actually like that there's lots of little experiments going on, trying any number of positions on all the little dials of society. Time will tell which ones work.

jfoster2• 11 years ago

Singapore is a different deal than most countries in the world. Perhaps free speech and civil liberties are not as strong there, but that trade-off gains them freedom from other things. Singaporeans are largely free from lots of types of crime that effectively plague many other first-world countries.

I think it would be nice if there were more countries that presented different types of trade-offs, and then some mechanism for people to decide what type of country they want to live in.

squeaky-clean• 11 years ago

It's funny, I have next to no knowledge on the current state of Singapore or it's politics. I have no idea what this man's political views are, or how well he has been leading. But seeing this code (and little bit of personality left in comments like the grandparent post) does make me like the PM more, as a person and a leader. It's not really rational, but it's the truth.

I guess I finally understand the whole "I want a president I could play sports / grab a beer / whatever with" sentiment.

crocowhile• 11 years ago

No country in the world has real free speech, whereby free speech means you can say whatever you want without going to jail (or to guantanamo).

dropit_sphere• 11 years ago

You wouldn't want to be accused of censoring code, would you?

ilija139• 11 years ago

As a foreigner living for 2 years in Singapore and coming from an unstable country I can say that Singaporeans have more freedom than any other citizens in the world. Like Mr. Calvin Cheng says:

"I tell you what freedom is.

Freedom is being able to walk on the streets unmolested in the wee hours in the morning, to be able to leave one's door open and not fear that one would be burgled. Freedom is the woman who can ride buses and trains alone; freedom is not having to avoid certain subway stations after night falls. Freedom is knowing our children can go to school without fear of drugs, or being mowed down by some insane person with a gun. Freedom is knowing that we are not bound by our class, our race, our religion, and we can excel for the individuals that we are - the freedom to accomplish. Freedom is living in one of the least corrupt societies in the world, knowing that our ability to get things done is not going to be limited by our ability to pay someone. Freedom is fresh air and clean streets, because nothing is more inimical to our liberty of movement than being trapped at home because of suffocating smog.

These are the freedoms that Singaporeans have, freedoms that were built on the vision and hard work of Mr Lee, our first Prime Minister. And we have all of these, these liberties, while also being one of the richest countries in the world."

The whole article is great http://www.straitstimes.com/news/singapore/more-singapore-st...

wheregotla• 11 years ago

American living in Singapore. For me, it's all about economic stability and employment opportunities, the two things I found lacking in US. I graduated in late 2000s in US and it was a really hard time for me. It was especially disappointing later to find that no one was even prosecuted.

"Well, at least our country has freedom of speech, brah!"

Yeah, no. I'd rather live in a country that provides a good living for its citizens and doesn't squander its wealth war mongering around the world for the sake of protecting some vague notions of "freedoms".

xwintermutex• 11 years ago

Looks more like C than idiomatic C++ at a first glance.

experimental-• 11 years ago

A very quick glance suggests to me that the only thing C++ specific there is the filename extension (although a C compiler would do a more thorough check than I do; and faster, even!)

unscaled2• 11 years ago

And the single-line comments, if not using a C99-compliant compiler. I wouldn't be surprised if he was using Visual C++ and had to change the extension to support a comment syntax that doesn't make you want to strangle yourself.

tcholas• 11 years ago

Was going to comment exactly the same thing

kachnuv_ocasek• 11 years ago

By the way, supposedly, he wrote this "years ago".

Keyframe• 11 years ago

Globals and, more serious offense, braces on newline!

mmahemoff• 11 years ago

Context from his speech: http://www.pmo.gov.sg/mediacentre/transcript-speech-prime-mi...

Previously on HN: https://news.ycombinator.com/item?id=9419035

hiby007• 11 years ago

Cool PM to have :)

Spooky23• 11 years ago

Meanwhile, in the U.S. a president barely has the ability to access a computer due to the ridiculous regulations surrounding them.

niyazpk• 11 years ago

Details please?

peter303• 11 years ago

Can any of the 20-some candidates for 2016 code? (Not that it is important.)

lugus352• 11 years ago

Buffer overflow on line 83. Input length is not checked but it must not be more than 79 characters long.

lugus352• 11 years ago

Sudoku2.cpp: In function 'void PrintStats()': Sudoku2.cpp:98:12: warning: unused variable 'j' [-Wunused-variable] int i, j, S; ^

Theodores• 11 years ago

Clinton could play the Saxophone, after that I am struggling to think of any politicians able to demonstrate a useful skill.

Programming might not be that hard to pick up if you had done it before, couldn't this code have been written on a 25 year old computer to compile with a Borland era compiler?

Because the wider population don't understand programming and see it as magic, I fully expect his popularity to do well, he is practically a hacker in their eyes, able to conjure up magic and demonstrate skill.

DanBC• 11 years ago

Margeret Thatcher was a chemist. She's variously credited with inventing "raspberry ripple" icecream, or "Mr Whippy" soft-serve style icecream. (The last one is definitely not true, it was invented a long time before she started working).

eru2• 11 years ago

Angela Merkel has a PhD in physical chemistry.

userbinator• 11 years ago

demonstrate a useful skill

Speaking in public (especially to very large crowds) and not turning into a nervous wreck is not a useful skill?

k-mcgrady• 11 years ago

> "Because the wider population don't understand programming and see it as magic, I fully expect his popularity to do well, he is practically a hacker in their eyes, able to conjure up magic and demonstrate skill."

The general public don't think of you as some sort of magic hacker because you code for a living, sorry.

Lrigikithumer3• 11 years ago

... he didn't imply they did

roel_v• 11 years ago

Vladimir Putin is a bona fide Judo expert. I guess it's debatable how 'useful' that is - just like playing the sax.

"Because the wider population don't understand programming and see it as magic, I fully expect his popularity to do well, he is practically a hacker in their eyes, able to conjure up magic and demonstrate skill."

The circle jerking in this thread rubs me the wrong way - "this guy must be awesome, he can pass a 1st year 'introduction to computer programming' class!". Must be the cognitive dissonance - there are people still saying Hans Reiser was surely framed, because how could a programmer be anything but God's gift to mankind?

emodendroket5• 11 years ago

Many politicians are former lawyers and it seems to me like passing a bar exam is a pretty useful skill (more useful than playing the sax, even) if you're going to endeavor to make laws.

kiiski• 11 years ago

Out of curiosity I checked what kind of degrees Finnish presidents have had. There was (not in any particular order):

  3 law, doctor
  2 law, master
  2 law, candidate (~bachelor)
  1 agriculture, doctor
  1 social sciences, doctor
  1 none, farmer + bank manager
  1 military, field marshal 
  1 teacher (primary school)

trequartista• 11 years ago

Manmohan Singh (former PM of India) was an economist par excellence. As the finance minister, he was responsible for the liberalization of the Indian economy and arguably responsible for the economic boom in the country today. But his tenure as a Prime Minister is largely remembered for his missteps and his general nonchalance to everything that happened around him. His legacy was tarnished and now he is just remembered as a puppet PM.

So yeah, extra curricular skills and fancy degrees and academic credentials may not translate into a good leader of the country.

zedadex• 11 years ago

What a fascinating world this will be.

blakecaldwell• 11 years ago

Can someone (less lazy than me) try running it against this puzzle?

http://www.telegraph.co.uk/news/science/science-news/9359579...

It's been over a year since I've thought about solving sudoku, but here's how I solved it then:

https://github.com/wblakecaldwell/c-sudoku-solver

pegler• 11 years ago

https://gist.github.com/pegler/752ae571c5d6028ebe72

Row[1] : 800000000

Row[2] : 003600000

Row[3] : 070090200

Row[4] : 050007000

Row[5] : 000045700

Row[6] : 000100030

Row[7] : 001000068

Row[8] : 008500010

Row[9] : 090000400

8-- --- ---

--3 6-- ---

-7- -9- 2--

-5- --7 ---

--- -45 7--

--- 1-- -3-

--1 --- -68

--8 5-- -1-

-9- --- 4--

812 753 649

943 682 175

675 491 283

154 237 896

369 845 721

287 169 534

521 974 368

438 526 917

796 318 452

Level Counts:

(8, 7): 1 (7, 7): 2 (7, 2): 3 (7, 5): 5 (2, 2): 7 (6, 2): 11

(1, 2): 20 (1, 7): 33 (6, 7): 51 (4, 7): 62 (2, 7): 86 (5, 2): 114

(8, 2): 160 (5, 3): 195 (5, 8): 217 (5, 9): 260 (5, 1): 317 (5, 4): 371

(4, 8): 398 (4, 9): 456 (6, 9): 473 (6, 1): 440 (6, 3): 429 (6, 5): 407

(6, 6): 392 (4, 3): 364 (4, 1): 360 (7, 6): 330 (7, 1): 302 (2, 1): 264

(7, 4): 229 (8, 5): 200 (4, 5): 164 (1, 5): 134 (2, 5): 115 (2, 6): 92

(1, 6): 71 (3, 6): 63 (4, 4): 47 (1, 3): 41 (8, 6): 37 (3, 4): 28

(3, 1): 20 (8, 9): 15 (2, 9): 12 (2, 8): 7 (1, 8): 4 (3, 9): 4

(3, 8): 1 (8, 1): 1 (1, 9): 1 (9, 1): 1 (1, 4): 1 (9, 3): 1

(9, 4): 1 (9, 5): 1 (9, 6): 1 (3, 3): 1 (9, 8): 1 (9, 9): 1

Count = 7826

Total Count = 13080

taeric• 11 years ago

Decided to try this puzzle against an implementation of the DLX algorithm I put up a while back.[1] Looks at 2,825 board states, in total. If I stop it at the solution, only looks at 1,489 states.

[1] http://taeric.github.io/Sudoku.html

dragonbonheur3• 11 years ago

Now, could someone with his age and experience get a job in Silicon Valley? The answer is precisely what is wrong in today's tech firms. Ageism must die.

eru2• 11 years ago

He has a lot of experience in management positions, and was the Senior Wrangler in Cambridge. I bet you dollars to donuts he could get a job in SV.

dragonbonheur3• 11 years ago

Not him specifically, someone of the same age or even 10 years younger and same experience in C++ programming.

Lrigikithumer3• 11 years ago

People with agendas making aggressive comments on barely related subjects to incite arguments which accomplish nothing are precisely what is wrong with todays online discussion.

unfunco• 11 years ago

Yes. Absolutely.

Experience managing the resources of a population of 5.5 million, experience on the world stage, programming and problem solving ability, his alma mater include Cambridge and Harvard, and military service, able to maintain close relationships with important people (including the President of the United States.)

He would absolutely get a job in Silicon Valley.

dragonbonheur3• 11 years ago

He would, sure. But does anyone care about the thousands that have been dismissed due to their age?

yincrash• 11 years ago

Is there proof that this is his?

codeulike• 11 years ago

He was the top of his year in Mathematics at Cambridge, which is pretty damn hardcore. So its definitely feasible that he could bang out some C++ code.

Gigablah2• 11 years ago

Posted on his official Twitter account: https://twitter.com/leehsienloong/status/595166789660647426

kenrick952• 11 years ago

He posted on Facebook, with screenshot of DevCpp.

https://www.facebook.com/leehsienloong/photos/a.344710778924...

Lrigikithumer3• 11 years ago

Capitalised identifiers? Global variables? Inconsistent indentation? PM of Singapore needs a better style guide.

rikf• 11 years ago

This is awesome and I don't wanna hate but the question has to be asked why c++?

There are tens more languages that are more modern and "aspirational"

noipv4• 11 years ago

Short of getting whipped, even the PM will learn to code. <sarcasm>

whizzkid2• 11 years ago

Little bit off topic but, Google Drive is giving me 500 error.

It was long time ago I read that Google was directly rejecting the CVs that have typos in them which I find it annoying and not nice. And today I see this title typo in their error page which is totally fine and a mistake that i also make sometimes (leaving shift button little early while pressing 1)

<title>Error 500 (Server Error)!!1</title>

"For Google — a company that sees 50,000 résumés a week — the typo is one of five résumé mistakes that will immediately land yours in the "no" pile." [0]

http://www.businessinsider.com/google-resume-mistake-2014-9?...

Human beings will make mistakes Google, there is no need to extremely force it to otherwise.

schrodinger• 11 years ago

I would suspect that was intentional.

whizzkid2• 11 years ago

hmm, when i think about it now, maybe it was!!1

Gigablah2• 11 years ago

It's deliberate. One of those "internet culture" things. Engineers are allowed to have a bit of humour sometimes.

daveid• 11 years ago

!!1 and variations thereof are intentional, it's a joke about being so excited you can't hold shift any longer.

amelius• 11 years ago

What strategy is this solver using? Is it a brute-force approach? Are there heuristics used?

vasilipupkin• 11 years ago

I think it's neat and could draw more people to CS, but yeah, people, let's not get overexcited over this. Knowing how to write a Sudoku solver in C++ says nothing, positive or negative about him as a prime minister

balabaster3• 11 years ago

I've been a (reasonably successful) programmer for 20+ years and I don't even know how to play Sudoku, nor does learning interest me... not being able to write a Sudoku solver bears no resemblance on ones capabilities. This goes the same as being able to write one. So I agree, getting excited about this seems somewhat... irrelevant. Being able to write any kind of computer program doesn't demonstrate being capable of effective leadership. Having a compelling vision for one's country, understanding the issues you will need to overcome to get there and inspiring the people to help you take it there are far more relevant to me.

Knowing a bit of C++ and understanding an algorithm to make it solve a puzzle is largely useless in this context. Understanding a bit about technology at (close to) the lowest level, doesn't signify an understanding of how the internet works, how encryption systems work, how network security or the communications infrastructure works. Without an understanding of these in today's world of the communications and the internet, you may as well not understand how to program at all. Where we see technology failing the people (certainly in North America) are because legislators are largely incompetent in this context and seek to protect corporate interests over the needs of the people. I would say, being a systems administrator or systems analyst would make you far more capable of understanding the implications of technical bills and regulations than understanding a bit of C++.

rustyrubygone• 11 years ago

Politicians and important folk recognise the power and awesomeness of C++, and don't waste time on Ruby, Go, Rust or other time waster languages!

edpichler• 11 years ago

For people who are criticizing this, try to find something good on it: it's just a curiosity about a powerful man of a well succeed country, that can inspire someone.

This also can be considered as a positive fact for me, once in my country, it's common to find politicians that even doesn't have any degree (including a very recent president).

PM of Singapore Shares His C++ Sudoku Solver Source Code

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