1 ! Copyright (c) 2007-2008 Aaron Schaefer.
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: arrays kernel make math math.functions math.matrices math.miller-rabin
4 math.order math.parser math.primes.factors math.ranges math.ratios
5 sequences sorting strings unicode.case parser accessors vocabs.parser
6 namespaces vocabs words quotations prettyprint ;
7 IN: project-euler.common
9 ! A collection of words used by more than one Project Euler solution
10 ! and/or related words that could be useful for future problems.
12 ! Problems using each public word
13 ! -------------------------------
14 ! alpha-value - #22, #42
15 ! cartesian-product - #4, #27, #29, #32, #33, #43, #44, #56
19 ! nth-triangle - #12, #42
20 ! number>digits - #16, #20, #30, #34, #35, #38, #43, #52, #55, #56, #92
21 ! palindrome? - #4, #36, #55
22 ! pandigital? - #32, #38
23 ! pentagonal? - #44, #45
24 ! propagate-all - #18, #67
25 ! sum-proper-divisors - #21
27 ! [uad]-transform - #39, #75
30 : nth-pair ( seq n -- nth next )
33 : perfect-square? ( n -- ? )
38 : max-children ( seq -- seq )
39 [ dup length 1- [ nth-pair max , ] with each ] { } make ;
41 ! Propagate one row into the upper one
42 : propagate ( bottom top -- newtop )
43 [ over rest rot first2 max rot + ] map nip ;
45 : (sum-divisors) ( n -- sum )
46 dup sqrt >integer [1,b] [
47 [ 2dup mod 0 = [ 2dup / + , ] [ drop ] if ] each
48 dup perfect-square? [ sqrt >fixnum neg , ] [ drop ] if
51 : transform ( triple matrix -- new-triple )
52 [ 1array ] dip m. first ;
56 : alpha-value ( str -- n )
57 >lower [ CHAR: a - 1+ ] sigma ;
59 : cartesian-product ( seq1 seq2 -- seq1xseq2 )
60 [ [ 2array ] with map ] curry map concat ;
65 : mediant ( a/c b/d -- (a+b)/(c+d) )
66 2>fraction [ + ] 2bi@ / ;
68 : max-path ( triangle -- n )
70 2 cut* first2 max-children [ + ] 2map suffix max-path
75 : number>digits ( n -- seq )
76 [ dup 0 = not ] [ 10 /mod ] produce reverse nip ;
78 : number-length ( n -- m )
79 log10 floor 1+ >integer ;
81 : nth-triangle ( n -- n )
84 : palindrome? ( n -- ? )
85 number>string dup reverse = ;
87 : pandigital? ( n -- ? )
88 number>string natural-sort >string "123456789" = ;
90 : pentagonal? ( n -- ? )
91 dup 0 > [ 24 * 1+ sqrt 1+ 6 / 1 mod zero? ] [ drop f ] if ;
93 ! Not strictly needed, but it is nice to be able to dump the triangle after the
95 : propagate-all ( triangle -- new-triangle )
96 reverse [ first dup ] [ rest ] bi
97 [ propagate dup ] map nip reverse swap suffix ;
99 : sum-divisors ( n -- sum )
100 dup 4 < [ { 0 1 3 4 } nth ] [ (sum-divisors) ] if ;
102 : sum-proper-divisors ( n -- sum )
103 dup sum-divisors swap - ;
105 : abundant? ( n -- ? )
106 dup sum-proper-divisors < ;
108 : deficient? ( n -- ? )
109 dup sum-proper-divisors > ;
111 : perfect? ( n -- ? )
112 dup sum-proper-divisors = ;
114 ! The divisor function, counts the number of divisors
116 group-factors flip second 1 [ 1+ * ] reduce ;
118 ! Optimized brute-force, is often faster than prime factorization
121 [ perfect-square? -1 0 ? ]
122 [ dup sqrt >fixnum [1,b] ] tri* [
123 dupd mod 0 = [ [ 2 + ] dip ] when
126 ! These transforms are for generating primitive Pythagorean triples
127 : u-transform ( triple -- new-triple )
128 { { 1 2 2 } { -2 -1 -2 } { 2 2 3 } } transform ;
129 : a-transform ( triple -- new-triple )
130 { { 1 2 2 } { 2 1 2 } { 2 2 3 } } transform ;
131 : d-transform ( triple -- new-triple )
132 { { -1 -2 -2 } { 2 1 2 } { 2 2 3 } } transform ;
136 [ name>> "-main" append create-in ] keep
137 [ drop in get vocab (>>main) ]
138 [ [ . ] swap prefix (( -- )) define-declared ]