Singapore's Prime Minister Shares His C++ Sudoku Solver Code

itwbennett writes: Several weeks ago, during a speech at the Founders Forum Smart Nation Singapore Reception, Singapore's prime minister Lee Hsien Loong said that he used to enjoy programming, and that the last program he wrote was a Sudoku solver in C++. To back that up, earlier today he announced (on Facebook and Twitter) that his code is available to download. He wrote on Facebook that he wrote the program 'several years ago' and that the code does 'a backtrack search, choosing the next cell to guess which minimises the fanout.'

Comments

Put in context

[Anonymous Coward]

The guy was a Senior Wrangler (top math undergrad) at Cambridge before going to governance. I would hope he'd have picked up some coding skills along the way.

Now with some other leaders, I'm impressed when they spell their names right.

Re: Put in context

[Anonymous Coward]

Wiki link to those who aren't across Cambridge lingo

http://en.m.wikipedia.org/wiki/Senior_Wrangler_%28University_of_Cambridge%29

The Senior Wrangler is the top mathematics undergraduate at Cambridge University in England, a position once regarded as "the greatest intellectual achievement attainable in Britain."

The actual code

[Anonymous Coward]

How's about including a link to the actual code?

Here you go:

https://drive.google.com/folde...

OR:

https://github.com/Doppp/LHL-S...

From his Facebook post on his Sudoku solver

[cciRRus]

He posted this on his Facebook.

For techies: the program does a backtrack search, choosing the next cell to guess which minimises the fanout.

Here’s a question for those reading the source code: if x is an (binary) integer, what does (x & -x) compute?

Hope you have fun playing with this. Please tell me if you find any bugs! – LHL

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As several of you noted, (x & –x) returns the least significant ‘1’ bit of x, i.e. the highest power of two that divides x. This assumes two’s complement notation for negative numbers, as some of you also pointed out. e.g. if x=12 (binary 1100), then (x & -x) = 4 (binary 100). I didn’t invent this; it is an old programming trick.

Nice!

Re:From his Facebook post on his Sudoku solver

[Anonymous Coward]

Not among prime ministers

New competition

[viperidaenz]

There should be an international coding competition between heads of state.

Re:Stupid sudoku solver?

[antiperimetaparalogo]

It might be a 'stupid sudoku solver', like you say, but at least, that is a program that does something, rather than the congress critters who do nothing but producing massive amount of HOT AIR

Imagine that you are a zombie apocalypse survivor, naked and wet, in a freezing winter Alaskan night, tired to death, and you can share a tent either with this Singapore's prime minister who wants you to stay awake with him and solve stupid Sudoku puzzles or with one of those "congress critters who do nothing but producing massive amount of HOT AIR" - who would be you choice?