small C puzzles

[madhav_a_kelkar]

i was browsing this problem:

The following is a piece of C code, whose intention was to print a
minus sign 20 times. But you can notice that, it doesn't work.

#include <stdio.h>
int main()
{
int i;
int n = 20;
for( i = 0; i < n; i-- )
printf("-");
return 0;
}

Well fixing the above code is straight-forward. To make the problem
interesting, you have to fix the above code, by changing exactly one
character. There are three known solutions. See if you can get all
those three.
one solution is to use n-- instead of i--. please let me know the
other two.

[William L. Bahn]

<ma************ *@hotmail.com> wrote in message
news:33******** *************** **@posting.goog le.com...

i was browsing this problem:

The following is a piece of C code, whose intention was to print a minus sign 20 times. But you can notice that, it doesn't work.

#include <stdio.h>
int main()
{
int i;
int n = 20;
for( i = 0; i < n; i-- )
printf("-");
return 0;
}

Well fixing the above code is straight-forward. To make the problem interesting, you have to fix the above code, by changing exactly one character. There are three known solutions. See if you can get all those three.
one solution is to use n-- instead of i--. please let me know the other two.

Sure....Tell the obvious one...;)

One is to change i < n to -i < n

Using ~i will almost work - and would on an implementation that
uses one's compliment.

The other is to change the test to i + n

Good little logic puzzle.

[Randy Howard]

In article <10************ *@corp.supernew s.com>, wi*****@toomuch spam.net
says...

<ma************ *@hotmail.com> wrote in message
news:33******** *************** **@posting.goog le.com...

i was browsing this problem:

The following is a piece of C code, whose intention was to

print a

minus sign 20 times. But you can notice that, it doesn't work.

#include <stdio.h>
int main()
{
int i;
int n = 20;
for( i = 0; i < n; i-- )
printf("-");
return 0;
}

Well fixing the above code is straight-forward. To make the

problem

interesting, you have to fix the above code, by changing

exactly one

character. There are three known solutions. See if you can get

all

those three.
one solution is to use n-- instead of i--. please let me know

the

other two.

Sure....Tell the obvious one...;)

One is to change i < n to -i < n

Using ~i will almost work - and would on an implementation that
uses one's compliment.

The other is to change the test to i + n

Good little logic puzzle.

Except, as Dan pointed out in the "earlier" version of this same thing
it still is guaranteed to work in the form above.

--
Randy Howard
To reply, remove FOOBAR.

[anonymous]

> one solution is to use n-- instead of i--. please let me know the

other two.

One more:

for (i = 0; ~i < n; i--)

Using bitwise negation.

[Christopher Benson-Manica]

ma************* @hotmail.com spoke thus:

Well fixing the above code is straight-forward. To make the problem
interesting, you have to fix the above code, by changing exactly one
character. There are three known solutions. See if you can get all
those three.

<pedantry>Actua lly, as stated, the problem is impossible - the
solutions involve *inserting* a character; I read "changing" to be an
operation that can be done in replace mode in one's editor of
choice.</pedantry>

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Robert Gamble]

On Wed, 01 Sep 2004 17:17:22 +0000, Christopher Benson-Manica wrote:

ma************* @hotmail.com spoke thus:

Well fixing the above code is straight-forward. To make the problem
interesting, you have to fix the above code, by changing exactly one
character. There are three known solutions. See if you can get all
those three.

<pedantry>Actua lly, as stated, the problem is impossible - the
solutions involve *inserting* a character; I read "changing" to be an
operation that can be done in replace mode in one's editor of
choice.</pedantry>

Which of the 3 solutions requires inserting a character instead of
changing a chracater, or can your editor not change a space character to
something else?

Rob Gamble

[Christopher Benson-Manica]

Robert Gamble <ro**********@h otmail.com> spoke thus:

Which of the 3 solutions requires inserting a character instead of
changing a chracater, or can your editor not change a space character to
something else?

Being pedantic is no fun when you turn out to be wrong... although
changing a space to a non-space would destroy the stylistic unity of
the program, so I'll take a smidgen of solace from that. Sorry.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Keith Thompson]

Christopher Benson-Manica <at***@nospam.c yberspace.org> writes:

ma************* @hotmail.com spoke thus:

Well fixing the above code is straight-forward. To make the problem
interesting, you have to fix the above code, by changing exactly one
character. There are three known solutions. See if you can get all
those three.

<pedantry>Actua lly, as stated, the problem is impossible - the
solutions involve *inserting* a character; I read "changing" to be an
operation that can be done in replace mode in one's editor of
choice.</pedantry>

The solutions involving changing "i" to "-i" or "~i" can be done by
replacing the preceding space.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Bigdakine]

>Subject: Re: small C puzzles

From: Christopher Benson-Manica at***@nospam.cy berspace.org
Date: 9/1/04 7:17 AM Hawaiian Standard Time
Message-id: <ch*********@ch essie.cirr.com>

ma************ *@hotmail.com spoke thus:

Well fixing the above code is straight-forward. To make the problem
interesting, you have to fix the above code, by changing exactly one
character. There are three known solutions. See if you can get all
those three.

<pedantry>Actu ally, as stated, the problem is impossible - the
solutions involve *inserting* a character; I read "changing" to be an
operation that can be done in replace mode in one's editor of
choice.</pedantry>

Now you tell me.

Stuart
Dr. Stuart A. Weinstein
Ewa Beach Institute of Tectonics
"To err is human, but to really foul things up requires a creationist"
"Creationis ts aren't impervious to Logic: They're oblivious to it."

[William L. Bahn]

"anonymous" <iu*********@ya hoo.co.in> wrote in message
news:f7******** *************** ***@posting.goo gle.com...

one solution is to use n-- instead of i--. please let me know the other two.

One more:

for (i = 0; ~i < n; i--)

Using bitwise negation.

On the vast majority of machines, this will not produce the
intended results since bitwise negation and multiplying by
negative one are not the same thing.