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From: lucio@proxima.UUCP (Lucio de Re)
Newsgroups: comp.lang.c
Subject: Re: Brain Teaser
Message-ID: <1272@proxima.UUCP>
Date: 7 Apr 90 11:55:03 GMT
References: <10289@wpi.wpi.edu>
Reply-To: lucio@proxima.UUCP (Lucio de Re)
Organization: FLAGSHIP Wide Area Networks - Cape Town
Lines: 25

In article <10289@wpi.wpi.edu> oesterle@wpi.wpi.edu (Shawn H. Oesterle) writes:
>Problem:
>        Swap two pointers without using a third pointer.
>Hint:
>        Two numbers may be swaped without using any other memory by executing
>        the following statements:
> 
>        int x, y;       /* or you can chose double, long, etc. */
> 
>        x += y;
>        y = x - y;
>        x -= y;

Well, I'd never have thought of it, thanks. Might be useful when
programming the i8051. As for the pointers swap, I suppose you
can't do the same because you need an integer in the middle. Maybe
a cast will save you, but is it worth it (or portable?).

----------------------------------------------------------------------
I used to design nuclear reactors and you should see the code that
engineers and scientists come up with. Yuuuck! Spaghetti everywhere.
-------------------------------------------------- (Kenneth L Moore) -
Lucio de Re                        ...uunet!ddsw1!olsa99!proxima!lucio
-------------------------------------------------------- lucio@proxima
                Disclaimer: He must have been joking!