Algorithm of this program is very easy − START Step 1 → Take integer variable A Step 2 → Assign value to the variable Step 3 → From value A upto 1 multiply each digit and store Step 4 → the final stored value is factorial of A STOP.
Factorial of a positive integer (number) is the sum of multiplication of all the integers smaller than that positive integer. For example, factorial of 5 is 5 * 4 * 3 * 2 * 1 which equals to 120.
So, I wrote a polyglot which works in the three languages I often write in, as well as one from my other answer to this question and one I just learned today. It's a standalone program, which reads a single line containing a nonnegative integer and prints a single line containing its factorial. Bignums are used in all languages, so the maximum computable factorial depends only on your computer's resources.
perl FILENAME
.runhugs FILENAME
or your favorite compiler's equivalent.g++ -lgmpxx -lgmp -x c++ FILENAME
to link against the right libraries. After compiling, run ./a.out
. Or use your favorite compiler's equivalent.bf < FILENAME > EXECUTABLE
. Make the output executable and run it. Or use your favorite distribution.wspace FILENAME
.Edit: added Whitespace as a fifth language. Incidentally, do not wrap the code with <code>
tags; it breaks the Whitespace. Also, the code looks much nicer in fixed-width.
char //# b=0+0{- |0*/; #>>>>,----------[>>>>,-------- #define a/*#--]>>>>++<<<<<<<<[>++++++[<------>-]<-<<< #Perl ><><><> <> <> <<]>>>>[[>>+<<-]>>[<<+>+>-]<-> #C++ --><><> <><><>< > < > < +<[>>>>+<<<-<[-]]>[-] #Haskell >>]>[-<<<<<[<<<<]>>>>[[>>+<<-]>>[<<+>+>-]>>] #Whitespace >>>>[-[>+<-]+>>>>]<<<<[<<<<]<<<<[<<<< #brainf*ck > < ]>>>>>[>>>[>>>>]>>>>[>>>>]<<<<[[>>>>*/ exp; ;//;#+<<<<-]<<<<]>>>>+<<<<<<<[<<<<][.POLYGLOT^5. #include <gmpxx.h>//]>>>>-[>>>[>>>>]>>>>[>>>>]<<<<[>> #define eval int main()//>+<<<-]>>>[<<<+>>+>-> #include <iostream>//<]<-[>>+<<[-]]<<[<<<<]>>>>[>[>>> #define print std::cout << // > <+<-]>[<<+>+>-]<<[>>> #define z std::cin>>//<< +<<<-]>>>[<<<+>>+>-]<->+++++ #define c/*++++[-<[-[>>>>+<<<<-]]>>>>[<<<<+>>>>-]<<*/ #define abs int $n //>< <]<[>>+<<<<[-]>>[<<+>>-]]>>]< #define uc mpz_class fact(int $n){/*<<<[<<<<]<<<[<< use bignum;sub#<<]>>>>-]>>>>]>>>[>[-]>>>]<<<<[>>+<<-] z{$_[0+0]=readline(*STDIN);}sub fact{my($n)=shift;#>> #[<<+>+>-]<->+<[>-<[-]]>[-<<-<<<<[>>+<<-]>>[<<+>+>+*/ uc;if($n==0){return 1;}return $n*fact($n-1); }//;# eval{abs;z($n);print fact($n);print("\n")/*2;};#-]<-> '+<[>-<[-]]>]<<[<<<<]<<<<-[>>+<<-]>>[<<+>+>-]+<[>-+++ -}-- <[-]]>[-<<++++++++++<<<<-[>>+<<-]>>[<<+>+>-++ fact 0 = 1 -- ><><><>< > <><>< ]+<[>-<[-]]>]<<[<<+ + fact n=n*fact(n-1){-<<]>>>>[[>>+<<-]>>[<<+>+++>+-} main=do{n<-readLn;print(fact n)}-- +>-]<->+<[>>>>+<<+ {-x<-<[-]]>[-]>>]>]>>>[>>>>]<<<<[>+++++++[<+++++++>-] <--.<<<<]+written+by+++A+Rex+++2009+.';#+++x-}--x*/;}
sorry I couldn't resist xD
HAI
CAN HAS STDIO?
I HAS A VAR
I HAS A INT
I HAS A CHEEZBURGER
I HAS A FACTORIALNUM
IM IN YR LOOP
UP VAR!!1
TIEMZD INT!![CHEEZBURGER]
UP FACTORIALNUM!!1
IZ VAR BIGGER THAN FACTORIALNUM? GTFO
IM OUTTA YR LOOP
U SEEZ INT
KTHXBYE
This is one of the faster algorithms, up to 170!. It fails inexplicably beyond 170!, and it's relatively slow for small factorials, but for factorials between 80 and 170 it's blazingly fast compared to many algorithms.
curl http://www.google.com/search?q=170!
There's also an online interface, try it out now!
Let me know if you find a bug, or faster implementation for large factorials.
This algorithm is slightly slower, but gives results beyond 170:
curl http://www58.wolframalpha.com/input/?i=171!
It also simplifies them into various other representations.
Uses the classic enum hack.
template<unsigned int n>
struct factorial {
enum { result = n * factorial<n - 1>::result };
};
template<>
struct factorial<0> {
enum { result = 1 };
};
Usage.
const unsigned int x = factorial<4>::result;
Factorial is calculated completely at compile time based on the template parameter n. Therefore, factorial<4>::result is a constant once the compiler has done its work.
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