Contributing for large number factorial

100+ Python challenging programming exercises.txt

@@ -52,13 +52,50 @@ Hints:
 In case of input data being supplied to the question, it should be assumed to be a console input.
 
 Solution:
-def fact(x):
-    if x == 0:
-        return 1
-    return x * fact(x - 1)
+# Python program to compute factorial 
+# of big numbers 
+
+import sys 
+def factorial( n) : 
+	res = [None]*500
+	# Initialize result 
+	res[0] = 1
+	res_size = 1
+
+	x = 2
+	while x <= n : 
+		res_size = multiply(x, res, res_size) 
+		x = x + 1
+
+	print ("Factorial of given number is") 
+	i = res_size-1
+	while i >= 0 : 
+		sys.stdout.write(str(res[i])) 
+		sys.stdout.flush() 
+		i = i - 1
+
+
+def multiply(x, res,res_size) : 
+
+	carry = 0 # Initialize carry  
+	i = 0
+	while i < res_size : 
+		prod = res[i] *x + carry 
+		res[i] = prod % 10; # Store last digit of 
+							# 'prod' in res[] 
+		carry = prod/10; # Put rest in carry 
+		i = i + 1
+
+	# Put carry in res and increase result size 
+	while (carry) : 
+		res[res_size] = carry % 10
+		carry = carry / 10
+		res_size = res_size + 1
+
+	return res_size 
+
+print factorial(n) 
 
-x=int(raw_input())
-print fact(x)
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