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| -rwxr-xr-x | challenge-224/jo-37/perl/ch-2.pl | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/challenge-224/jo-37/perl/ch-2.pl b/challenge-224/jo-37/perl/ch-2.pl new file mode 100755 index 0000000000..e9fe9f88e8 --- /dev/null +++ b/challenge-224/jo-37/perl/ch-2.pl @@ -0,0 +1,94 @@ +#!/usr/bin/perl -s + +use v5.24; +use Test2::V0; +use experimental 'signatures'; + +our ($tests, $examples, $verbose); + +run_tests() if $tests || $examples; # does not return + +die <<EOS unless @ARGV == 1 && length $ARGV[0] > 2; +usage: $0 [-examples] [-tests] [-verbose] [STR] + +-examples + run the examples from the challenge + +-tests + run some tests + +-verbose + show the found additive sequence instead of a true / false result + +STR + a string of decimal digits having a minimum length of three + +EOS + + +### Input and Output + +say $verbose ? + "(@{is_additive(@ARGV) // []})" : + is_additive(@ARGV) ? 'true' : 'false'; + + +### Implementation + +# The task states: "An additive number is a string whose digits can form +# an additive sequence." I see some ambiguity in the phrase "digits can +# form an additive sequence". What is the meaning of "form"? We might +# pick arbitrary digits to build numbers. However, the examples suggest +# that we shall split the given string to get the numbers. As this +# interpretation significantly simplifies the task, I'll follow it. +# +# The first two numbers may be chosen freely from the head of the +# string. However, there are restrictions to their lengths: +# - The maximum length of the first number must leave enough room for a +# second number of length one and a tail of the same length as the +# first number. +# - The maximum length of the second number must leave enough room for a +# tail of the lengths of both, the first and the second number. +# Starting with all starting pairs conforming to above restrictions, we +# check if the remaining string follows the additive sequence generated +# by the starting pair. Collecting the additive sequence along the way. + +sub is_additive ($s) { + my $l = length $s; + for (my $lx = 1; 2 * $lx + 1 <= $l; $lx++) { + for (my $ly = 1; 2 * $lx + $ly <= $l && $lx + 2 * $ly <= $l; $ly++) { + my $x = substr $s, 0, $lx; + my $y = substr $s, $lx, $ly; + my $z = $x + $y; + my @seq = ($x, $y); + ($x, $y, $z) = ($y, $z, $y + $z, push @seq, $z) + while $s =~ /\G$x(?=$y$z)/gc; # set "pos" between x and y + return \@seq if $s =~ /\G$x$y$/g; + } + } + undef; +} + + +### Examples and tests + +sub run_tests { + SKIP: { + skip "examples" unless $examples; + + is is_additive(112358), [qw(1 1 2 3 5 8)], 'example 1'; + ok !is_additive(12345), 'example 2'; + is is_additive(199100199), [qw(1 99 100 199)], 'example 3'; + } + + SKIP: { + skip "tests" unless $tests; + + is is_additive(11112111311152228), [qw(1111 2 1113 1115 2228)], + 'a bit longer'; + is is_additive('011'), [qw(0 1 1)], 'leading zero'; + } + + done_testing; + exit; +} |