1 USING: arrays kernel math math.functions math.miller-rabin math.matrices
2 math.order math.parser math.primes.factors math.ranges namespaces
3 sequences sequences.lib sorting unicode.case ;
4 IN: project-euler.common
6 ! A collection of words used by more than one Project Euler solution
7 ! and/or related words that could be useful for future problems.
9 ! Problems using each public word
10 ! -------------------------------
11 ! alpha-value - #22, #42
12 ! cartesian-product - #4, #27, #29, #32, #33, #43, #44, #56
13 ! collect-consecutive - #8, #11
16 ! nth-triangle - #12, #42
17 ! number>digits - #16, #20, #30, #34, #35, #38, #43, #52, #55, #56
18 ! palindrome? - #4, #36, #55
19 ! pandigital? - #32, #38
20 ! pentagonal? - #44, #45
21 ! propagate-all - #18, #67
22 ! sum-proper-divisors - #21
24 ! [uad]-transform - #39, #75
27 : nth-pair ( n seq -- nth next )
28 over 1+ over nth >r nth r> ;
30 : perfect-square? ( n -- ? )
35 : count-shifts ( seq width -- n )
38 : max-children ( seq -- seq )
39 [ dup length 1- [ over nth-pair max , ] each ] { } make nip ;
41 ! Propagate one row into the upper one
42 : propagate ( bottom top -- newtop )
43 [ over rest rot first2 max rot + ] map nip ;
45 : shift-3rd ( seq obj obj -- seq obj obj )
48 : (sum-divisors) ( n -- sum )
49 dup sqrt >fixnum [1,b] [
50 [ 2dup mod zero? [ 2dup / + , ] [ drop ] if ] each
51 dup perfect-square? [ sqrt >fixnum neg , ] [ drop ] if
54 : transform ( triple matrix -- new-triple )
55 [ 1array ] dip m. first ;
59 : alpha-value ( str -- n )
60 >lower [ CHAR: a - 1+ ] sigma ;
62 : cartesian-product ( seq1 seq2 -- seq1xseq2 )
63 swap [ swap [ 2array ] map-with ] map-with concat ;
65 : collect-consecutive ( seq width -- seq )
67 2dup count-shifts [ 2dup head shift-3rd , ] times
73 : max-path ( triangle -- n )
75 2 cut* first2 max-children [ + ] 2map suffix max-path
80 : number>digits ( n -- seq )
81 [ dup zero? not ] [ 10 /mod ] [ ] produce reverse nip ;
83 : nth-triangle ( n -- n )
86 : palindrome? ( n -- ? )
87 number>string dup reverse = ;
89 : pandigital? ( n -- ? )
90 number>string natural-sort "123456789" = ;
92 : pentagonal? ( n -- ? )
93 dup 0 > [ 24 * 1+ sqrt 1+ 6 / 1 mod zero? ] [ drop f ] if ;
95 ! Not strictly needed, but it is nice to be able to dump the triangle after the
97 : propagate-all ( triangle -- newtriangle )
98 reverse [ first dup ] keep rest [ propagate dup ] map nip reverse swap suffix ;
100 : sum-divisors ( n -- sum )
101 dup 4 < [ { 0 1 3 4 } nth ] [ (sum-divisors) ] if ;
103 : sum-proper-divisors ( n -- sum )
104 dup sum-divisors swap - ;
106 : abundant? ( n -- ? )
107 dup sum-proper-divisors < ;
109 : deficient? ( n -- ? )
110 dup sum-proper-divisors > ;
112 : perfect? ( n -- ? )
113 dup sum-proper-divisors = ;
115 ! The divisor function, counts the number of divisors
117 group-factors flip second 1 [ 1+ * ] reduce ;
119 ! Optimized brute-force, is often faster than prime factorization
121 factor-2s [ 1+ ] dip [ perfect-square? -1 0 ? ] keep
122 dup sqrt >fixnum [1,b] [
123 dupd mod zero? [ [ 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 ;