Factorial: Difference between revisions
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{{task}}[[Category:Recursion]]The '''Factorial Function''' is the product of |
{{task}}[[Category:Recursion]]The '''Factorial Function''' of a positive integer, n, is defined as the product of the sequence n, n-1, n-2, ...1 and the factorial of zero, 0, is [[http://en.wikipedia.org/wiki/Factorial#Definition defined]] as being 1. |
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Write a function to return the factorial of a number. Solutions can be iterative or recursive (though recursive solutions are generally considered too slow and are mostly used as an exercise in recursion). Support for negative n errors is optional. |
Write a function to return the factorial of a number. Solutions can be iterative or recursive (though recursive solutions are generally considered too slow and are mostly used as an exercise in recursion). Support for trapping negative n errors is optional. |
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==References== |
==References== |
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Revision as of 06:20, 17 August 2008
You are encouraged to solve this task according to the task description, using any language you may know.
The Factorial Function of a positive integer, n, is defined as the product of the sequence n, n-1, n-2, ...1 and the factorial of zero, 0, is [defined] as being 1.
Write a function to return the factorial of a number. Solutions can be iterative or recursive (though recursive solutions are generally considered too slow and are mostly used as an exercise in recursion). Support for trapping negative n errors is optional.
References
Ada
Iterative
<Ada> function Factorial (N : Positive) return Positive is
Result : Positive := N; Counter : Natural := N - 1;
begin
for I in reverse 1..Counter loop
Result := Result * I;
end loop;
return Result;
end Factorial; </Ada>
Recursive
<Ada> function Factorial(N : Positive) return Positive is
Result : Positive := 1;
begin
if N > 1 then
Result := N * Factorial(N - 1);
end if;
return Result;
end Factorial; </Ada>
ALGOL 68
Iterative
PROC factorial = (INT in n)LONG LONG INT:(
INT n := in n;
LONG LONG INT z := n;
WHILE n>1 DO
n -:= 1;
z *:= n
OD;
z
)
Recursive
PROC factorial = (INT n)LONG LONG INT:
CASE n+1 IN
1,1,2,6,24,120,720 # a brief lookup #
OUT
n*factorial(n-1)
ESAC
;
Python
Iterative
<python>def factorial(n):
z=n
while n>1:
n=n-1
z=z*n
return z
</python>
Recursive
<python>def factorial(n):
z=1
if n>1:
z=n*factorial(n-1)
return z
</python>