Factorial problems solved in Ruby and C Lang

Author: vhbsouza

factorial/factorial.c

@@ -0,0 +1,46 @@
+/*
+	Observation: 
+
+		C Language doesn't have native support to Big Integer numbers,
+		so on a x86 processor the maximum factorial number that can be reached is 12
+		and on a x86_64 is 20.
+
+		If you need to use big integer numbers, I recommend you search about the OpenSSL Big Numbers library.
+		http://www.openssl.org/docs/crypto/bn.html
+
+		To print a `unsigned long int` number use `%lu` on prinf() function.
+
+*/
+
+#include "stdio.h"
+
+// Interative Loop
+unsigned long int factorial (unsigned short int number){
+	unsigned long int factorial = 1;
+	unsigned short int i=2;
+
+	do {
+		factorial *= i++;
+	} while (i<=number);
+	return factorial;
+}
+
+// Interative Reverse Loop
+unsigned long int factorialReverse (unsigned short int number){
+	unsigned long int factorial = 1;
+	unsigned short int i;
+
+	for (i = number; i > 0; i--){
+		factorial *= i;
+	}
+	return factorial;
+}
+
+// Recursive
+unsigned long int factorialRecursive(unsigned short int number){
+	if (number==1) {
+		return 1;
+	} else {
+		return number * factorialRecursive(number-1);
+	}
+}

factorial/factorial.rb

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+class Integer
+
+  # Iterative
+  def factorial_simple number
+    fat = 1
+    for n in 2..number do 
+      fat = fat * n
+    end
+    fat
+  end
+
+  # Iterative Reverse Loop
+  def factorial_reverse number
+    (n-1).downto(1).each {|i| n *= i}
+    n
+  end
+
+  # Recursive - Ternary Operator
+  def factorial_recursive number
+    (number == 1)? 1: (number * factorial_recursive(number-1))      
+  end
+
+  # The Ruby-iest version, using reduce function
+  def factorial_reduce(number)
+    (1..number).reduce(:*)
+  end
+
+  alias_method :factorial :factorial_reduce
+end