Update: When I wrote my original solution to this problem, I overlooked the requirement to ignore out-of-order numerals. The code below now checks for this (I also made some other minor changes). Thanks to Roy Johnson for the heads-up!
Update 2: Animator informs me that the new version of the code still fails (it does not give the desired output for "XIX", for example). (Thanks!) . I have updated the code to show the failures.
On further thought, I think that this part of the spec is ambiguous:
I want to ignore characters that are "out of order" (the "I" in "IV") but allow subsequent matches of characters that are in order (the "V" in "IV").
...since it does not specify why it is the "I" and not the "V" that should be regarded as the out of order numeral. Why is "X" the desired output for "XL", but "V" the desired output for "IV"? The case of "XIX" is also problematic, because both "X" or "I" may be regarded as out of order (depending on how one chooses to interpret this specification), and yet the desired output for "XIX" is "....X.I". What should the output be for "VIX"? Or for "DLXVIM"?
I don't think that regexes are the tool for this job:
use strict;
use warnings;
my %pos;
@pos{ qw( M D C L X V I ) } = ( 0 .. 6 );
my $n_keys = keys %pos;
my $template = '.' x $n_keys;
while ( <DATA> ) {
my ( $in, $desired) = split;
my $out = $template;
my $ptr = $n_keys;
for my $i ( reverse ( 0 .. length( $in ) - 1 ) ) {
my $c = substr $in, $i, 1;
if ( $pos{ $c } < $ptr ) {
substr( $out, $pos{ $c }, 1 ) = $c;
$ptr = $pos{ $c };
}
}
print "$in\t=> $out\t", ( $out eq $desired ? '' : 'not ' ), 'ok', $/
+;
}
__DATA__
I ......I
IV .....V.
V .....V.
VI .....VI
IX ....X..
X ....X..
XI ....X.I
XIV ....XV.
XV ....XV.
XVI ....XVI
XIX ....X.I
X ....X..
XL ....X..
LX ...LX..
XC ....X..
CLXIX ..CLX.I
CDXLVI .D..XVI
MCMXCVI M.C.XVI
MDCLI MDCL..I
__END__
I => ......I ok
IV => .....V. ok
V => .....V. ok
VI => .....VI ok
IX => ....X.. ok
X => ....X.. ok
XI => ....X.I ok
XIV => ....XV. ok
XV => ....XV. ok
XVI => ....XVI ok
XIX => ....X.. not ok
X => ....X.. ok
XL => ...L... not ok
LX => ...LX.. ok
XC => ..C.... not ok
CLXIX => ..CLX.. not ok
CDXLVI => .D.L.VI not ok
MCMXCVI => M.C..VI not ok
MDCLI => MDCL..I ok
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.