Solution for Project Euler problem 20

extra/project-euler/020/020.factor

@@ -0,0 +1,25 @@
+! Copyright (c) 2007 Aaron Schaefer.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel math.combinatorics math.parser sequences ;
+IN: project-euler.020
+
+! http://projecteuler.net/index.php?section=problems&id=20
+
+! DESCRIPTION
+! -----------
+
+! n! means n * (n - 1) * ... * 3 * 2 * 1
+
+! Find the sum of the digits in the number 100!
+
+
+! SOLUTION
+! --------
+
+: euler020 ( -- answer )
+    100 factorial number>string string>digits sum ;
+
+! [ euler020 ] 100 ave-time
+! 0 ms run / 0 ms GC ave time - 100 trials
+
+MAIN: euler020

extra/project-euler/project-euler.factor

@@ -6,7 +6,8 @@ USING: io io.files kernel math.parser namespaces sequences strings
     project-euler.005 project-euler.006 project-euler.007 project-euler.008
     project-euler.009 project-euler.010 project-euler.011 project-euler.012
     project-euler.013 project-euler.014 project-euler.015 project-euler.016
-    project-euler.017 project-euler.018 project-euler.019 project-euler.067 ;
+    project-euler.017 project-euler.018 project-euler.019 project-euler.020
+    project-euler.067 ;
 IN: project-euler
 
 <PRIVATE