40 lines
952 B
Factor
40 lines
952 B
Factor
! Copyright (c) 2008 Aaron Schaefer.
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: combinators.short-circuit kernel math.parser math.ranges
|
|
project-euler.common sequences ;
|
|
IN: project-euler.036
|
|
|
|
! http://projecteuler.net/index.php?section=problems&id=36
|
|
|
|
! DESCRIPTION
|
|
! -----------
|
|
|
|
! The decimal number, 585 = 1001001001 (binary), is palindromic in both bases.
|
|
|
|
! Find the sum of all numbers, less than one million, which are palindromic in
|
|
! base 10 and base 2.
|
|
|
|
! (Please note that the palindromic number, in either base, may not include
|
|
! leading zeros.)
|
|
|
|
|
|
! SOLUTION
|
|
! --------
|
|
|
|
! Only check odd numbers since the binary number must begin and end with 1
|
|
|
|
<PRIVATE
|
|
|
|
: both-bases? ( n -- ? )
|
|
{ [ palindrome? ] [ >bin dup reverse = ] } 1&& ;
|
|
|
|
PRIVATE>
|
|
|
|
: euler036 ( -- answer )
|
|
1 1000000 2 <range> [ both-bases? ] filter sum ;
|
|
|
|
! [ euler036 ] 100 ave-time
|
|
! 1703 ms ave run time - 96.6 SD (100 trials)
|
|
|
|
MAIN: euler036
|