Solution to Project Euler problem 56

extra/project-euler/056/056.factor

@@ -0,0 +1,31 @@
+! Copyright (c) 2008 Aaron Schaefer.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel math.functions math.ranges project-euler.common sequences ;
+IN: project-euler.056
+
+! http://projecteuler.net/index.php?section=problems&id=56
+
+! DESCRIPTION
+! -----------
+
+! A googol (10^100) is a massive number: one followed by one-hundred zeros;
+! 100^100 is almost unimaginably large: one followed by two-hundred zeros.
+! Despite their size, the sum of the digits in each number is only 1.
+
+! Considering natural numbers of the form, a^b, where a, b < 100, what is the
+! maximum digital sum?
+
+
+! SOLUTION
+! --------
+
+! Through analysis, you only need to check when a and b > 90
+
+: euler056 ( -- answer )
+    90 100 [a,b) dup cartesian-product
+    [ first2 ^ number>digits sum ] map supremum ;
+
+! [ euler056 ] 100 ave-time
+! 33 ms run / 1 ms GC ave time - 100 trials
+
+MAIN: euler056

extra/project-euler/project-euler.factor

@@ -14,8 +14,9 @@ USING: definitions io io.files kernel math math.parser project-euler.ave-time
     project-euler.037 project-euler.038 project-euler.039 project-euler.040
     project-euler.041 project-euler.042 project-euler.043 project-euler.044
     project-euler.045 project-euler.048 project-euler.052 project-euler.053
-    project-euler.067 project-euler.075 project-euler.079 project-euler.097
-    project-euler.134 project-euler.169 project-euler.173 project-euler.175 ;
+    project-euler.056 project-euler.067 project-euler.075 project-euler.079
+    project-euler.097 project-euler.134 project-euler.169 project-euler.173
+    project-euler.175 ;
 IN: project-euler
 
 <PRIVATE