Factorial

[Sang-drax]

Also, an 2^32-1 input will overflow on the result unless provisions are also made for big numbers, even for 64bit computers, won't it?

Then you have to be more clever than that, won't you?

[Sang-drax]

Here's my submission. It is password protected, btw, so no need to cheat.

[foxman]

Alright, thanks for participating Sang-drax. Don't forget to publish the password the day the contest ends.

I would like to add that when I say it has to be in C/C++, inline assembly is also accepted (of course), as long as it's incorporated through a C/C++ program and compile on gcc and run on the target architecture. And for those who would like this extra information:

sizeof(int) = 4
sizeof(long) = 8

[abachler]

ok, so an array of ~21 million bytes shoudl suffice to hold the largest value you specified (1 million), although 2^32-1 would require around 205 gigabytes of ram just for teh answer, so Im going to go ahead and just assume you wont give an input larger than 1 million. At that rate, assuming you can get the multiply for free adn just have to transfer the answer each iteration, adn only once, you are lookign at around 80+ minutes run time for 1000000!

[whiteflags]

I wasn't joking when I said that there were optimizations for large N, obviously. These are algorithm changes too, not just unrolling loops or something like that.