1 USING: arrays kernel math math.functions math.miller-rabin
2 math.matrices math.order math.parser math.primes.factors
3 math.ranges namespaces make sequences sequences.lib sorting
5 IN: project-euler.common
7 ! A collection of words used by more than one Project Euler solution
8 ! and/or related words that could be useful for future problems.
10 ! Problems using each public word
11 ! -------------------------------
12 ! alpha-value - #22, #42
13 ! cartesian-product - #4, #27, #29, #32, #33, #43, #44, #56
14 ! collect-consecutive - #8, #11
17 ! nth-triangle - #12, #42
18 ! number>digits - #16, #20, #30, #34, #35, #38, #43, #52, #55, #56
19 ! palindrome? - #4, #36, #55
20 ! pandigital? - #32, #38
21 ! pentagonal? - #44, #45
22 ! propagate-all - #18, #67
23 ! sum-proper-divisors - #21
25 ! [uad]-transform - #39, #75
28 : nth-pair ( n seq -- nth next )
29 over 1+ over nth >r nth r> ;
31 : perfect-square? ( n -- ? )
36 : count-shifts ( seq width -- n )
39 : max-children ( seq -- seq )
40 [ dup length 1- [ over nth-pair max , ] each ] { } make nip ;
42 ! Propagate one row into the upper one
43 : propagate ( bottom top -- newtop )
44 [ over rest rot first2 max rot + ] map nip ;
46 : shift-3rd ( seq obj obj -- seq obj obj )
49 : (sum-divisors) ( n -- sum )
50 dup sqrt >fixnum [1,b] [
51 [ 2dup mod zero? [ 2dup / + , ] [ drop ] if ] each
52 dup perfect-square? [ sqrt >fixnum neg , ] [ drop ] if
55 : transform ( triple matrix -- new-triple )
56 [ 1array ] dip m. first ;
60 : alpha-value ( str -- n )
61 >lower [ CHAR: a - 1+ ] sigma ;
63 : cartesian-product ( seq1 seq2 -- seq1xseq2 )
64 swap [ swap [ 2array ] map-with ] map-with concat ;
66 : collect-consecutive ( seq width -- seq )
68 2dup count-shifts [ 2dup head shift-3rd , ] times
74 : max-path ( triangle -- n )
76 2 cut* first2 max-children [ + ] 2map suffix max-path
81 : number>digits ( n -- seq )
82 [ dup zero? not ] [ 10 /mod ] [ ] produce reverse nip ;
84 : nth-triangle ( n -- n )
87 : palindrome? ( n -- ? )
88 number>string dup reverse = ;
90 : pandigital? ( n -- ? )
91 number>string natural-sort "123456789" = ;
93 : pentagonal? ( n -- ? )
94 dup 0 > [ 24 * 1+ sqrt 1+ 6 / 1 mod zero? ] [ drop f ] if ;
96 ! Not strictly needed, but it is nice to be able to dump the triangle after the
98 : propagate-all ( triangle -- newtriangle )
99 reverse [ first dup ] keep rest [ propagate dup ] map nip reverse swap suffix ;
101 : sum-divisors ( n -- sum )
102 dup 4 < [ { 0 1 3 4 } nth ] [ (sum-divisors) ] if ;
104 : sum-proper-divisors ( n -- sum )
105 dup sum-divisors swap - ;
107 : abundant? ( n -- ? )
108 dup sum-proper-divisors < ;
110 : deficient? ( n -- ? )
111 dup sum-proper-divisors > ;
113 : perfect? ( n -- ? )
114 dup sum-proper-divisors = ;
116 ! The divisor function, counts the number of divisors
118 group-factors flip second 1 [ 1+ * ] reduce ;
120 ! Optimized brute-force, is often faster than prime factorization
122 factor-2s [ 1+ ] dip [ perfect-square? -1 0 ? ] keep
123 dup sqrt >fixnum [1,b] [
124 dupd mod zero? [ [ 2 + ] dip ] when
127 ! These transforms are for generating primitive Pythagorean triples
128 : u-transform ( triple -- new-triple )
129 { { 1 2 2 } { -2 -1 -2 } { 2 2 3 } } transform ;
130 : a-transform ( triple -- new-triple )
131 { { 1 2 2 } { 2 1 2 } { 2 2 3 } } transform ;
132 : d-transform ( triple -- new-triple )
133 { { -1 -2 -2 } { 2 1 2 } { 2 2 3 } } transform ;