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Comment: From his Facebook post on his Sudoku solver (Score 5, Interesting) 230

by cciRRus (#49617631) Attached to: Singapore's Prime Minister Shares His C++ Sudoku Solver Code
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


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.


Comment: Human *FLESH* Search is correct! (Score 1) 109

by cciRRus (#48127535) Attached to: China Bans "Human Flesh Searching"
No, "flesh" is NOT a racist typo! That is the direct translation of the actual Chinese phrase "ren rou sou suo".

ren rou: human flesh
sou suo: search

The idea is simply to leverage on the wide viewership of Internet communities (i.e.g forums and BBSes) to search or identify the actual "human flesh" responsible for the atrocities depicted in viral videos.

Comment: Skyjack only works for WiFi drones! (Score 4, Informative) 161

by cciRRus (#45590327) Attached to: How To Hijack a Drone For $400 In Less Than an Hour
While pro-grade multicopters like those to be deployed by Amazon operate at 2.4GHz, they do not use WiFi as their radio system! Typically, these multicopters are fitted radio systems such as Futaba, JR, Spektrum or 9X, and therefore Skyjack will not be able to take them down.

Comment: Limited Android Market (Score 1) 278

by cciRRus (#38279608) Attached to: Sub-$100 Android 4.0 Tablet Coming Soon
Not only that the price is expensive after factoring in the shipping charges, this tablet is MIPS-based, so it will have a very limited Android Market. Take note!

The tablet to get is actually Ainol Novo 7 Advanced, not the Novo 7 Basic stated in the article. The 7A has a much better hardware. It is widely believed that the Novo7A will get ICS real soon as there are videos of it running ICS circulating in the chinese forums.