You're handling the input as an array, which is fine, but if you take a string of characters instead it can be useful to know that there is a neat trick to check whether $derange is a derangement of $string:

  if (($derange ^ $string) !~ /\0/) {
    print "'$derange' is a derangement\n";
  }
[download]

I suspect there is a way to solve the complete problem for strings using a single s/// substitution to generate the "next" permutation (starting with a Unicodabetically-sorted string), but I don't see an easy way to do it off the top of my head - you need to replace the character preceding the longest reverse-sorted trailing substring with the next available character and sort what's left, which sounds likely to involve some fairly ugly (??{...}) code.

Hugo

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.