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Add alternate solution to Project Euler problem #2

db4
Aaron Schaefer 2008-12-02 00:46:38 -05:00
parent 0ef3ff4058
commit 46911bc797
2 changed files with 30 additions and 2 deletions
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1
extra/project-euler/002/002-tests.factor
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@ -3,3 +3,4 @@ IN: project-euler.002.tests
[ 4613732 ] [ euler002 ] unit-test
[ 4613732 ] [ euler002a ] unit-test
[ 4613732 ] [ euler002b ] unit-test

31
extra/project-euler/002/002.factor
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@ -1,4 +1,4 @@
! Copyright (c) 2007 Aaron Schaefer, Alexander Solovyov.
! Copyright (c) 2007, 2008 Aaron Schaefer, Alexander Solovyov, Vishal Talwar.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel math sequences shuffle ;
IN: project-euler.002
@ -50,4 +50,31 @@ PRIVATE>
! [ euler002a ] 100 ave-time
! 0 ms ave run time - 0.2 SD (100 trials)
MAIN: euler002a
<PRIVATE
: next-fibs ( x y -- y x+y )
tuck + ;
: ?retotal ( total fib- fib+ -- retotal fib- fib+ )
dup even? [ [ nip + ] 2keep ] when ;
: (sum-even-fibs-below) ( partial fib- fib+ max -- total )
2dup > [
3drop
] [
[ ?retotal next-fibs ] dip (sum-even-fibs-below)
] if ;
PRIVATE>
: sum-even-fibs-below ( max -- sum )
[ 0 0 1 ] dip (sum-even-fibs-below) ;
: euler002b ( -- answer )
4000000 sum-even-fibs-below ;
! [ euler002b ] 100 ave-time
! 0 ms ave run time - 0.0 SD (100 trials)
MAIN: euler002b