diff --git a/extra/project-euler/052/052.factor b/extra/project-euler/052/052.factor new file mode 100644 index 0000000000..3f6487fb3e --- /dev/null +++ b/extra/project-euler/052/052.factor @@ -0,0 +1,50 @@ +! Copyright (c) 2008 Aaron Schaefer. +! See http://factorcode.org/license.txt for BSD license. +USING: combinators.lib kernel math project-euler.common sequences sorting ; +IN: project-euler.052 + +! http://projecteuler.net/index.php?section=problems&id=52 + +! DESCRIPTION +! ----------- + +! It can be seen that the number, 125874, and its double, 251748, contain +! exactly the same digits, but in a different order. + +! Find the smallest positive integer, x, such that 2x, 3x, 4x, 5x, and 6x, +! contain the same digits. + + +! SOLUTION +! -------- + +! Analysis shows the number must be odd, divisible by 3, and larger than 123456 + +digits natural-sort ] map all-equal? ; + +: candidate? ( n -- ? ) + { [ dup odd? ] [ dup 3 mod zero? ] } && nip ; + +: next-all-same ( x n -- n ) + dup candidate? [ + 2dup swap map-nx all-same-digits? + [ nip ] [ 1+ next-all-same ] if + ] [ + 1+ next-all-same + ] if ; + +PRIVATE> + +: euler052 ( -- answer ) + 6 123456 next-all-same ; + +! [ euler052 ] 100 ave-time +! 403 ms run / 7 ms GC ave time - 100 trials + +MAIN: euler052 diff --git a/extra/project-euler/project-euler.factor b/extra/project-euler/project-euler.factor index 226c47b0a3..2f8a3184bb 100644 --- a/extra/project-euler/project-euler.factor +++ b/extra/project-euler/project-euler.factor @@ -12,9 +12,9 @@ USING: definitions io io.files kernel math math.parser project-euler.ave-time project-euler.029 project-euler.030 project-euler.031 project-euler.032 project-euler.033 project-euler.034 project-euler.035 project-euler.036 project-euler.037 project-euler.038 project-euler.039 project-euler.040 - project-euler.041 project-euler.042 project-euler.048 project-euler.067 - project-euler.075 project-euler.134 project-euler.169 project-euler.173 - project-euler.175 ; + project-euler.041 project-euler.042 project-euler.048 project-euler.052 + project-euler.067 project-euler.075 project-euler.134 project-euler.169 + project-euler.173 project-euler.175 ; IN: project-euler