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factor-puzzles/projecteuler/euler258/euler258.factor

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2020-11-29 08:22:10 +01:00
! Copyright (C) 2020 Bubbler.
! See http://factorcode.org/license.txt for BSD license.
USING: arrays grouping kernel locals math math.bits
math.functions math.polynomials prettyprint sequences ;
IN: projecteuler.euler258
: p-sq' ( poly -- poly' )
64 2^ swap polyval sq make-bits 64 group [ bits>number ] map ;
:: polykm ( poly k m -- poly' )
poly length 2 - k >= [ k 0 <array> 1 suffix ] [
poly k 2/ m polykm
p-sq' k odd? [ 0 prefix ] when
poly p/mod nip [ m mod ] map
] if ;
:: polykm-special ( n k m -- poly )
n 1 - k >= [ k 0 <array> 1 suffix ] [
n k 2/ m polykm-special
p-sq' k odd? [ 0 prefix ] when
2 [ n short cut dup 0 prefix p+ p+ ] times [ m mod ] map
] if ;
: euler258-slow ( n k m -- ans )
[ 2 - 0 <array> { -1 -1 } { 1 } surround ] 2dip
[ polykm sum ] keep mod ;
: euler258-fast ( n k m -- ans )
[ polykm-special sum ] keep mod ;
: euler258-main ( -- )
2000 10 18 ^ 20092010 euler258-fast . ;
MAIN: euler258-main