factor: trim using lists

[factor.git] / extra / project-euler / 085 / 085.factor

diff --git a/extra/project-euler/085/085.factor b/extra/project-euler/085/085.factor
index bd09203da568a65a3190aacc7fd9d2ef4e0ba921..3c04724c57184978cd95b864234f7af63cdd9bff 100644 (file)
--- a/extra/project-euler/085/085.factor
+++ b/extra/project-euler/085/085.factor
@@ -1,6 +1,7 @@
 ! Copyright (c) 2009 Guillaume Nargeot.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: arrays kernel math math.ranges project-euler.common sequences ;
+USING: accessors kernel math ranges project-euler.common
+sequences ;
 IN: project-euler.085
 
 ! http://projecteuler.net/index.php?section=problems&id=85
@@ -18,33 +19,36 @@ IN: project-euler.085
 ! SOLUTION
 ! --------
 
-! A grid measuring x by y contains x * (x + 1) * y * (x + 1) rectangles.
+! A grid measuring x by y contains x * (x + 1) * y * (x + 1) / 4 rectangles.
 
 <PRIVATE
 
 : distance ( m -- n )
-    2000000 - abs ;
+    2000000 - abs ; inline
 
 : rectangles-count ( a b -- n )
-    2dup [ 1 + ] bi@ * * * 4 / ;
+    2dup [ 1 + ] bi@ * * * 4 /i ; inline
 
-: unique-products ( a b -- seq )
-    tuck [a,b] [
-        over dupd [a,b] [ 2array ] with map
-    ] map concat nip ;
+:: each-unique-product ( ... a b quot: ( ... i j -- ... ) -- ... )
+    a b [a..b] [| i |
+        i b [a..b] [| j |
+            i j quot call
+        ] each
+    ] each ; inline
 
-: max-by-last ( seq seq -- seq )
-    [ [ last ] bi@ < ] most ;
+TUPLE: result { area read-only } { distance read-only } ;
 
-: array2 ( seq -- a b )
-    [ first ] [ last ] bi ;
+C: <result> result
 
-: convert ( seq -- seq )
-    array2 [ * ] [ rectangles-count distance ] 2bi 2array ;
+: min-by-distance ( seq seq -- seq )
+    [ [ distance>> ] bi@ < ] most ; inline
+
+: compute-result ( i j -- pair )
+    [ * ] [ rectangles-count distance ] 2bi <result> ; inline
 
 : area-of-nearest ( -- n )
-    1 2000 unique-products
-    [ convert ] [ max-by-last ] map-reduce first ;
+    T{ result f 0 2000000 } 1 2000
+    [ compute-result min-by-distance ] each-unique-product area>> ;
 
 PRIVATE>
 
@@ -52,6 +56,6 @@ PRIVATE>
     area-of-nearest ;
 
 ! [ euler085 ] 100 ave-time
-! 2285 ms ave run time - 4.8 SD (100 trials)
+! 791 ms ave run time - 17.15 SD (100 trials)
 
 SOLUTION: euler085