Solution to task 1

1 files changed, 81 insertions, 0 deletions

diff --git a/challenge-257/jo-37/perl/ch-1.pl b/challenge-257/jo-37/perl/ch-1.pl
new file mode 100755
index 0000000000..93bd7fb00c
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+++ b/challenge-257/jo-37/perl/ch-1.pl
@@ -0,0 +1,81 @@
+#!/usr/bin/perl -s
+
+use v5.24;
+use Test2::V0 '!float';
+use PDL;
+use PDL::NiceSlice;
+use Benchmark 'cmpthese';
+
+our ($tests, $examples, $benchmark);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [--] [N...]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N...
+    list of numbers
+
+EOS
+
+
+### Input and Output
+
+say sdc(@ARGV);
+
+
+### Implementation
+
+sub sdc {
+    my $l = long @_;
+    my $si = $l->qsorti;
+    cat($si, sequence($l) - $l->($si)->dummy(0)->enumvec)
+        ->xchg(0,1)->qsortvec->((1));
+}
+
+sub sdc_full {
+    my $l = long @_;
+    ($l < $l->dummy(0))->sumover;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is sdc(5, 2, 1, 6)->unpdl, [2, 1, 0, 3], 'example 1';
+        is sdc(1, 2, 0, 3)->unpdl, [1, 2, 0, 3], 'example 2';
+        is sdc(0, 1)->unpdl, [0, 1], 'example 3';
+        is sdc(9, 4, 9, 2)->unpdl, [2, 1, 2, 0], 'example 4';
+
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+    }
+
+    SKIP: {
+        skip "benchmark" unless $benchmark;
+
+        my $n = 10000;
+        my $l = ($n * random $n)->long;
+        ok all(sdc_full($l) == sdc($l)), 'cross-check';
+
+        cmpthese(0, {
+                full => sub {sdc_full($l)},
+                rank => sub {sdc($l)}
+            });
+
+    }
+
+    done_testing;
+    exit;
+}