1 ! Copyright (c) 2007-2009 Aaron Schaefer, Slava Pestov.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: kernel math math.functions ranges project-euler.common sequences
7 ! http://projecteuler.net/index.php?section=problems&id=1
12 ! If we list all the natural numbers below 10 that are multiples of 3 or 5, we
13 ! get 3, 5, 6 and 9. The sum of these multiples is 23.
15 ! Find the sum of all the multiples of 3 or 5 below 1000.
21 ! Inclusion-exclusion principle
25 : sum-divisible-by ( target n -- m )
26 [ /i dup 1 + * ] keep * 2 /i ;
30 : euler001 ( -- answer )
31 999 3 sum-divisible-by
32 999 5 sum-divisible-by +
33 999 15 sum-divisible-by - ;
35 ! [ euler001 ] 100 ave-time
36 ! 0 ms ave run time - 0.0 SD (100 trials)
42 : euler001a ( -- answer )
43 0 999 3 <range> sum 0 999 5 <range> sum + 0 999 15 <range> sum - ;
45 ! [ euler001a ] 100 ave-time
46 ! 0 ms ave run time - 0.03 SD (100 trials)
49 : euler001b ( -- answer )
50 1000 <iota> [ [ 5 mod ] [ 3 mod ] bi [ 0 = ] either? ] filter sum ;
52 ! [ euler001b ] 100 ave-time
53 ! 0 ms ave run time - 0.06 SD (100 trials)
56 : euler001c ( -- answer )
57 1000 <iota> [ { 3 5 } [ divisor? ] with any? ] filter sum ;
59 ! [ euler001c ] 100 ave-time
60 ! 0 ms ave run time - 0.06 SD (100 trials)
63 : euler001d ( -- answer )
64 { 3 5 } [ [ 999 ] keep <range> ] gather sum ;
66 ! [ euler001d ] 100 ave-time
67 ! 0 ms ave run time - 0.08 SD (100 trials)