Newsgroups: rec.puzzles
From: hoey@AIC.NRL.Navy.Mil (Dan Hoey)
Date: 29 Apr 92 21:16:42 GMT
Subject: Re: Counting down to 383, hints

vt87...@cc.tut.fi (Timonen Vesa) asked:

> Try to make 383 by using numbers: 1 2 25 50 75 100
> and operations: + - / * ()

Of course we are to use the numbers exactly once each, and it seems we
must use the operators zero or more times each; one of the operators
cannot be used nongratuitously.

I'm surprised no one has gotten this one yet, since the solution is of
a form that cuts down the search space quite a bit.  For us
brute-force hackers, it's an interesting experiment on the assumptions
our code makes: Many programmers would code the search to *only* look
at such expressions.  On the other hand, some programmers may have
made a different assumption, and ruled out the solution, which is
unique up to commutativity.  I made the assumption that the invisible
operator is not allowed, and that division is exact; perhaps those
have prevented me from seeing yet other solutions.

I won't post the answer now.  In fact, I'm concerned I might spoil
someone's homework or contest or bar bet were I to do so.  But if you
write the expression in its most regular way, with no spaces and with
traditional parenthesization, the /usr/5bin/sum program will fold it
to '946 1'.  Just so you know I got the answer.

Dan Hoey
Hoey@AIC.NRL.Navy.Mil