Solution to task 1

1 files changed, 103 insertions, 0 deletions

diff --git a/challenge-116/jo-37/perl/ch-1.pl b/challenge-116/jo-37/perl/ch-1.pl
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+++ b/challenge-116/jo-37/perl/ch-1.pl
@@ -0,0 +1,103 @@
+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [num]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+num
+   Number to be split into a successing sequence
+
+EOS
+
+
+### Input and Output
+
+say join ',', @{succ_seq(shift)};
+
+
+### Implementation
+
+# Splitting any kind of sequence into smaller subsequences preserves
+# their original order.  Assuming this interpretation in accordance with
+# the examples.
+# Furthermore, the difference between two consecutive parts shall always
+# be one, or in other words: each part (except the first) shall be the
+# successor of the previous.  As leading zeros are not allowed for a
+# part, every subsequent part is thus uniquely determined by its
+# predecessor.
+# Given that Perl's auto-increment operator acts on strings too,
+# excessively large numbers may be processed as long as they are
+# provided as strings.  See test cases.
+
+sub succ_seq {
+    local $_ = shift;
+    # As the input is taken as a string, leading zeros must be excluded,
+    # since    ++($_ = '01') eq '02'   is true.  Luckily this is a
+    # prerequisite in the task.
+    die "not valid\n" unless /^[1-9][0-9]+\z/;
+
+    # Try first parts that have half of the string's length at most.
+    for my $len (1 .. length() / 2) {
+        # Accept any first part having the current length.
+        my $part = qr/.{$len}/;
+
+        my @split;
+        while (/\G($part)/g) {
+            # Collect the matched part and take its successor as the
+            # next expected match.
+            push @split, ($part = $1)++;
+            # If the current match extends to the end of the string, the
+            # collected parts represent a solution.
+            return \@split if pos() == length();
+        }
+    }
+
+    # Default:
+    [$_];
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is succ_seq(1234), [1, 2, 3, 4], 'example 1';
+        is succ_seq(91011), [9, 10, 11], 'example 2';
+        is succ_seq(10203), [10203], 'example 3';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is succ_seq(9899100101), [98, 99, 100, 101], 'split around 100';
+        is succ_seq(999910000), [9999, 10000], 'split around 10000';
+        is succ_seq(1819202), [1819202], 'missing last digit';
+        is succ_seq(109), [109], 'out of sequence';
+        is succ_seq(1012), [1012], 'step too high';
+        like dies {succ_seq('0102')}, qr/not valid/,
+            'would falsely work on strings';
+
+        my @expected = ('9' x 99, '1' . '0' x 99);
+        is succ_seq(join '', @expected), \@expected, '199 digits in 2 parts';
+
+        @expected = 3 .. 103;
+        is succ_seq(join '', @expected), \@expected, '199 digits in 101 parts';
+	}
+
+    done_testing;
+    exit;
+}