Factor solution to project Euler problem 173

diff --git a/extra/project-euler/173/173.factor b/extra/project-euler/173/173.factor
new file mode 100644 (file)
index 0000000..4eef3ec
--- /dev/null
+++ b/extra/project-euler/173/173.factor
@@ -0,0 +1,34 @@
+! Copyright (c) 2007 Aaron Schaefer.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel math math.functions math.ranges sequences ;
+IN: project-euler.173
+
+! http://projecteuler.net/index.php?section=problems&id=173
+
+! DESCRIPTION
+! -----------
+
+! We shall define a square lamina to be a square outline with a square
+! "hole" so that the shape possesses vertical and horizontal
+! symmetry. For example, using exactly thirty-two square tiles we can
+! form two different square laminae: [see URL for figure]
+
+! With one-hundred tiles, and not necessarily using all of the tiles at
+! one time, it is possible to form forty-one different square laminae.
+
+! Using up to one million tiles how many different square laminae can be
+! formed?
+
+! SOLUTION
+! --------
+
+: laminaes ( upper -- n )
+  4 / dup sqrt [1,b] 0 rot [ over /mod drop - - ] curry reduce ;
+
+: euler173 ( -- answer )
+  1000000 laminaes ;
+
+! [ euler173 ] 100 ave-time
+! 0 ms run / 0 ms GC ave time - 100 trials
+
+MAIN: euler173

diff --git a/extra/project-euler/project-euler.factor b/extra/project-euler/project-euler.factor
index f256f031389a8ee397638e2badac0ff74ecb8426..68c71da049385282bcc5c55e740a0dac7d07ed78 100644 (file)
--- a/extra/project-euler/project-euler.factor
+++ b/extra/project-euler/project-euler.factor
@@ -10,7 +10,7 @@ USING: definitions io io.files kernel math math.parser sequences strings
     project-euler.067
                       project-euler.134
     project-euler.169
-                                        project-euler.175 ;
+    project-euler.173                   project-euler.175 ;
 IN: project-euler
 
 <PRIVATE