1 ! Copyright (c) 2007-2009 Aaron Schaefer, Slava Pestov.
2 ! See https://factorcode.org/license.txt for BSD license.
3 USING: kernel math math.functions ranges project-euler.common
7 ! https://projecteuler.net/problem=1
12 ! If we list all the natural numbers below 10 that are multiples
13 ! of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is
16 ! Find the sum of all the multiples of 3 or 5 below 1000.
22 ! Inclusion-exclusion principle
26 : sum-divisible-by ( target n -- m )
27 [ /i dup 1 + * ] keep * 2 /i ;
31 : euler001 ( -- answer )
32 999 3 sum-divisible-by
33 999 5 sum-divisible-by +
34 999 15 sum-divisible-by - ;
36 ! [ euler001 ] 100 ave-time
37 ! 0 ms ave run time - 0.0 SD (100 trials)
43 : euler001a ( -- answer )
44 0 999 3 <range> sum 0 999 5 <range> sum + 0 999 15 <range> sum - ;
46 ! [ euler001a ] 100 ave-time
47 ! 0 ms ave run time - 0.03 SD (100 trials)
50 : euler001b ( -- answer )
51 1000 <iota> [ [ 5 mod ] [ 3 mod ] bi [ 0 = ] either? ] filter sum ;
53 ! [ euler001b ] 100 ave-time
54 ! 0 ms ave run time - 0.06 SD (100 trials)
57 : euler001c ( -- answer )
58 1000 <iota> [ { 3 5 } [ divisor? ] with any? ] filter sum ;
60 ! [ euler001c ] 100 ave-time
61 ! 0 ms ave run time - 0.06 SD (100 trials)
64 : euler001d ( -- answer )
65 { 3 5 } [ [ 999 ] keep <range> ] gather sum ;
67 ! [ euler001d ] 100 ave-time
68 ! 0 ms ave run time - 0.08 SD (100 trials)