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#!/usr/bin/perl -s
use v5.24;
use Test2::V0 '!float';
use PDL;
our ($tests, $examples);
run_tests() if $tests || $examples; # does not return
die <<EOS unless @ARGV > 2;
usage: $0 [-examples] [-tests] [K N1 N2...]
-examples
run the examples from the challenge
-tests
run some tests
K
desired difference between two list elements
N1 N2...
list of numbers
EOS
### Input and Output
main: {
local $" = ',';
local $, = ',';
say map "(@$_)", diff_k(@ARGV)->@*;
}
### Implementation
# Take the difference of all pairs, invalidate the diagonal and find all
# matching indices.
sub diff_k {
my $k = shift;
my $l = long @_;
$l->badflag(1);
my $d = $l - $l->dummy(0);
$d->diagonal(0, 1) .= $d->badvalue;
whichND($d == $k)->unpdl;
}
### Examples and tests
sub run_tests {
SKIP: {
skip "examples" unless $examples;
is diff_k(2, 2,7,9), [[2, 1]], 'example';
}
SKIP: {
skip "tests" unless $tests;
is diff_k(0, 1,2,2), bag {item [1,2]; item [2,1]; end;}, 'i != j';
}
done_testing;
exit;
}
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