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#!/usr/local/bin/perl
use strict;
use warnings;
use feature qw(say);
use Test::More;
use Benchmark qw(cmpthese timethis);
use Data::Dumper qw(Dumper);
my @TESTS = (
[ 5, 1 ],
[ 4, 0 ],
[ 9, 1 ],
[ 90, 0 ],
[ 45, 1 ],
[ 15, 1 ],
[ 31, 1 ],
[ 63, 1 ],
[ 127, 1 ],
[ 255, 1 ],
[ 129, 1 ],
[ 65, 1 ],
[ 247, 0 ],
[ 200,0],
[ 500,0],
[ 100,0],
[ 400,0],
[ 300,0],
);
is( is_binary_palindrome($_->[0]), $_->[1] ) foreach @TESTS;
is( is_binary_palindrome_string($_->[0]), $_->[1] ) foreach @TESTS;
cmpthese( 100_000, {
'array' => sub { is_binary_palindrome($_->[0]) foreach @TESTS },
'string' => sub { is_binary_palindrome_string($_->[0]) foreach @TESTS },
} );
done_testing();
sub is_binary_palindrome_string {
## This is the core perl solution convert to binary using sprintf
## [this is faster than unpack and doesn't have issue with leading 0s!]
## and compare with reverse...
return ( ( $a = sprintf '%b', $_[0] ) eq reverse $a ) || 0;
}
sub is_binary_palindrome {
## Can we write an array based one which is faster! Answer NO!
## We work from both ends to see if the numbers are different
## if they are return 0
## o/w we get to the end and return 1
my @n = split m{}, sprintf '%b', shift;
(pop @n eq shift @n) || return 0 while @n > 1;
return 1;
}
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