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#!/usr/bin/env perl
###########################################################################
# script name: ch-2.pl #
# #
# https://github.com/user-person #
# #
# https://perlweeklychallenge.org/blog/perl-weekly-challenge-055/ #
# #
# Wave Array #
# Any array N of non-unique, unsorted integers can be arranged into a #
# wave-like array such that n1 => n2 <= n3 => n4 <= n5 and so on. #
# For example, given the array [1, 2, 3, 4], possible wave arrays #
# include [2, 1, 4, 3] or [4, 1, 3, 2], since 2 => 1 <= 4 => 3 <= #
# and 4 => 1 <= 3 => 2. This is not a complete list. #
# Write a script to print all possible wave arrays for an integer array #
# N of arbitrary length. #
# #
# Notes: #
# When considering N of any length, note that the first element is #
# always greater than or equal to the second, and then the <= => <= #
# sequence alternates until the end of the array. #
# #
###########################################################################
use strict;
use warnings;
use List::Permutor;
my @n = (1,2,3,4);
if (@ARGV) {
@n = ();
my $argString = "@ARGV";
my %pair = ( '[' => ']', '(' => '\)', '{' => '}', '<' => '>');
$argString =~ s{\A\s*([[(\{<])\s*}{};
$argString =~ s{\s*$pair{$1}\s*\Z}{} if $1;
$argString =~ s{[, ]+}{ }g;
foreach (split m{ }, $argString) {
if ($_ =~ m{\d+}) {
push @n, $_;
} else {
print STDERR "Non-numeric input detected.\n";
exit(1);
}
}
} else {
print STDERR "No arguments given. Using example data: [1, 2, 3, 4]\n";
}
my $perm = new List::Permutor @n;
ARRAY_LOOP:
while (my @set = $perm->next) {
my $prev;
ITEM_LOOP:
for (my $i = 0; $i <= $#set; ++$i) {
next ITEM_LOOP if $i == 0;
if ($i % 2 == 0) { # EVEN
next ARRAY_LOOP if $set[$i-1] > $set[$i];
} else { # ODD
next ARRAY_LOOP if $set[$i-1] < $set[$i];
}
}
print "$_ " foreach @set;
print "\n";
}
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