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# Programming Puzzle

I found these questions on a web site and wish to share with all of u
out there,Can SomeOne Solve these Porgramming puzzles.
Programming Puzzles

Some companies certainly ask for these things. Specially Microsoft.
Here are my favorite puzzles. Don't send me emails asking for the
solutions.

Q1 Write a "Hello World" program in 'C' without using a semicolon.
Q2 Write a C++ program without using any loop (if, for, while etc) to
print numbers from 1 to 100 and 100 to 1;
Q3 C/C++ : Exchange two numbers without using a temporary variable.
Q4 C/C++ : Find if the given number is a power of 2.
Q5 C/C++ : Multiply x by 7 without using multiplication (*) operator.
Q6 C/C++ : Write a function in different ways that will return f(7) =
4 and f(4) = 7
Q7 Remove duplicates in array
Q8 Finding if there is any loop inside linked list.
Q9 Remove duplicates in an no key access database without using an
array
Q10 Write a program whose printed output is an exact copy of the
source. Needless to say, merely echoing the actual source file is not
allowed.
Q11 From a 'pool' of numbers (four '1's, four '2's .... four '6's),
each player selects a number and adds it to the total. Once a number
is used, it must be removed from the pool. The winner is the person
whose number makes the total equal 31 exactly.
Q12 Swap two numbers without using a third variable.
Given an array (group) of numbers write all the possible sub groups of
this group.
Q14 Convert (integer) number in binary without loops.

Q3,12 are similar , Q7 is simple & I know there answer For the Rest
Nov 14 '05
271 20376
In <cr************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Julie <ju***@nospam.c om> wrote:
Irrwahn Grausewitz wrote:
Julie <ju***@nospam.c om> wrote:
>Irrwahn Grausewitz wrote:<snip> >> What would you call p and *p, respectively?
>>
>> int main(void)
>> {
>> int a = 1;
>> int *p = &a;
>> *p = 2;
>> return 0;
>> }
>
>I call 'p' a "pointer [to an int]" and '*p' "p dereferenced" or "a pointer [to
>an int] dereferenced".

So you think the term "variable" is applicable to neither p nor *p?

I'd call p a variable, but not *p.

I agree with you here.

How would you call *p, though? It has the semantics of a variable,
doesn't it?
I'd say that *p might /point/ to a
variable, but that is it.

I beg to differ, I'd rather say that p points to a variable.

That's something too subtle for Julie to understand. She seems to be
blind to the semantic difference between p (that can point to a variable)
and *p (that *is* the variable pointed to by p).

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de
Nov 14 '05 #221
In <gs************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Da*****@cern.c h (Dan Pop) wrote:
Irrwahn Grausewitz <ir*******@free net.de> writes:
Da*****@cern .ch (Dan Pop) wrote:<snip>As long as c.l.c is still an imperfect ivory tower (i.e. it still has
connectio ns with the real world) it is highly unrealistic to ignore
popular CS jargon terms like "variable" and "global", simply because the
C standard itself doesn't use them.

It's indeed highly unrealistic to expect everyone to avoid those
terms. However, a quick look in the archives shows that the use of
correct, well-defined terms, instead of sloppy jargon, serves well to
reduce the risk of confusion. What's wrong with object, external
linkage, file scope, etc.pp., after all?

Nothing, except that answering a newbie question in a jargon that is
completely unknown to him is not going to *really* help him.

Agreed, but it's IMHO likely to confuse newbies, if e.g. someone calls
a dereferenced pointer a variable, as happened up-thread.

I disagree. It's perfectly intuitive (unless you happen to be Julie):
p points to a variable and *p is the variable pointed to by p. Why would
a newbie be confused by the simplest thing about pointers in C?
Neither is
pointing him to the standard, so that he learns the "proper" terminology.

Definitly; it's much better to explain the "proper" terminology in
context. I consider this to be one (albeit not main) purpose of this
news-group.

When replying to a newbie question, you must consider the newbie's
priorities. Giving him a full lesson about the "proper" terminology
is not exactly what I call helpful. There is plenty of time to learn
the "proper" terminology later and most people have nothing to lose by
never learning it. Again, real world vs the ivory tower: I've been
programming for years without the slightest clue about the "proper"
terminology and the code written back then is still working...
If you really want to help a newbie, you *must* use the terminology he
understands . It's as simple as that, hence my reference to the perfect
ivory tower.

Fortunately, c.l.c will never become a perfect ivory tower, or at
the very least as long as I continue to post here... ;-)

Then, why are you arguing on the ivory tower side? ;-)

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de
Nov 14 '05 #222
pete wrote:

Julie wrote:

pete wrote:

Julie wrote:

> Please describe (in code) a situation where two
> variables share the same memory location.

In post
*node is a variable.
In the code example, *node has the same address as either

I meant:

"In the code example, *node has the same address as either

--
pete
Nov 14 '05 #223
Irrwahn Grausewitz wrote:

Julie <ju***@nospam.c om> wrote:
Irrwahn Grausewitz wrote:
Julie <ju***@nospam.c om> wrote:
>Irrwahn Grausewitz wrote: <snip> >> What would you call p and *p, respectively?
>>
>> int main(void)
>> {
>> int a = 1;
>> int *p = &a;
>> *p = 2;
>> return 0;
>> }
>
>I call 'p' a "pointer [to an int]" and '*p' "p dereferenced" or "a pointer [to
>an int] dereferenced".

So you think the term "variable" is applicable to neither p nor *p?

I'd call p a variable, but not *p.

I agree with you here.
I'd say that *p might /point/ to a
variable, but that is it.

I beg to differ, I'd rather say that p points to a variable.

In context specific conditions (such as the code above), this is true where p
points to a.

However (and it wasn't clear in my response), generally speaking: an arbitrary
point x *may* point to a variable, but not necessarily.
Nov 14 '05 #224
Dan Pop wrote:

In <cr************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Julie <ju***@nospam.c om> wrote:
Irrwahn Grausewitz wrote:
Julie <ju***@nospam.c om> wrote:
>Irrwahn Grausewitz wrote:

<snip>
>> What would you call p and *p, respectively?
>>
>> int main(void)
>> {
>> int a = 1;
>> int *p = &a;
>> *p = 2;
>> return 0;
>> }
>
>I call 'p' a "pointer [to an int]" and '*p' "p dereferenced" or "a pointer [to
>an int] dereferenced".

So you think the term "variable" is applicable to neither p nor *p?

I'd call p a variable, but not *p.

I agree with you here.

How would you call *p, though? It has the semantics of a variable,
doesn't it?
I'd say that *p might /point/ to a
variable, but that is it.

I beg to differ, I'd rather say that p points to a variable.

That's something too subtle for Julie to understand. She seems to be
blind to the semantic difference between p (that can point to a variable)
and *p (that *is* the variable pointed to by p).

Dan -- your condescending attitude benefits no one in this newsgroup, and only
selfishly serves you.

I was speaking in general terms, not specifically. In the case of the code
posted, *p does point to a variable a, but only in this specific case. In
general terms, a pointer x *may* point to a variable.

Here are some examples of pointers that do *not* point to variables:

int * x = NULL;

const int b = 123;
const int * w = &b;

int * r = &printer_port_o ut;
Nov 14 '05 #225

"Julie" <ju***@nospam.c om> wrote in message
news:40******** *******@nospam. com...
Dan Pop wrote:

In <cr************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Julie <ju***@nospam.c om> wrote:

That's something too subtle for Julie to understand. She seems to be blind to the semantic difference between p (that can point to a variable) and *p (that *is* the variable pointed to by p).
Dan -- your condescending attitude benefits no one in this

newsgroup, and only selfishly serves you.

It doesn't serve him very well. ;-)

Jonathan
Nov 14 '05 #226
Dan Pop wrote:
That's something too subtle for Julie to understand. She seems to be
blind to the semantic difference between p (that can point to a variable)
and *p (that *is* the variable pointed to by p).

Well, you and Julie actually use the term variable in the place of the
term object.
As the C++ standard says:

"A variable is introduced by the declaration of an object. The
variable’s name denotes the object."

"An object is a region of storage. [Note: A function is not an object,
regardless of whether or not it occupies storage in the way that objects
do. ] An object is created by a definition (3.1), by a new-expression
(5.3.4) or by the implementation (12.2) when needed."
So in terminology, a variable can only denote one object, which is
always different from another object.
The original question becomes "what if we pass the same object to the
swap function?".
If you do not use the correct terminology, you will never reach a
conclusion, since both of you use your own terminologies.
----

A pointer is a variable that denotes an object (which stores addresses).

A dereferenced pointer is not a variable (since it is not introduced by
the declaration of an object), but represents an object.
As I said, the original question becomes: "what if we pass the same
object to the swap function?".

It would be nice if you tried to communicate on this basis.

Regards,

Ioannis Vranos,

Language Lawyer :-)
Nov 14 '05 #227
Julie wrote:

Dan Pop wrote:

In <cr************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Julie <ju***@nospam.c om> wrote:
>Irrwahn Grausewitz wrote:
>> Julie <ju***@nospam.c om> wrote:
>> >Irrwahn Grausewitz wrote:
<snip>
>> >> What would you call p and *p, respectively?
>> >>
>> >> int main(void)
>> >> {
>> >> int a = 1;
>> >> int *p = &a;
>> >> *p = 2;
>> >> return 0;
>> >> }
>> >I'd call p a variable, but not *p.

I agree with you here.

How would you call *p, though? It has the semantics of a variable,
doesn't it?
>I'd say that *p might /point/ to a
>variable, but that is it.

I beg to differ, I'd rather say that p points to a variable.

That's something too subtle for Julie to understand.
She seems to be
blind to the semantic difference between p
(that can point to a variable)
and *p (that *is* the variable pointed to by p).

benefits no one in this newsgroup, and only
selfishly serves you.

I was speaking in general terms, not specifically.
In the case of the code posted,
*p does point to a variable a,

No it doesn't.
*p is an object of type int. It doesn't point anywhere.

--
pete
Nov 14 '05 #228
Da*****@cern.ch (Dan Pop) wrote:
In <gs************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
<snip>
Agreed, but it's IMHO likely to confuse newbies, if e.g. someone calls
a dereferenced pointer a variable, as happened up-thread.

I disagree. It's perfectly intuitive (unless you happen to be Julie):
p points to a variable and *p is the variable pointed to by p. Why would
a newbie be confused by the simplest thing about pointers in C?

IMO we should agree to disagree: *p is not a proper identifier and it
can't be initialized on declaration, thus it's not a variable. *p is
the contents of the memory location p points to, converted to the type
p is a pointer to.

<snip>
Definitly; it's much better to explain the "proper" terminology in
context. I consider this to be one (albeit not main) purpose of this
news-group.

When replying to a newbie question, you must consider the newbie's
priorities. Giving him a full lesson about the "proper" terminology
is not exactly what I call helpful.

Is your world really black and white only? There's not a great void
between a simple explanation and an exhaustive lecture in applied
Standardese. A comprehensible explanation, enriched with some
for that matter) is what I'd call not only helpful, but educative,
too.
There is plenty of time to learn
the "proper" terminology later and most people have nothing to lose by
never learning it. Again, real world vs the ivory tower: I've been
programming for years without the slightest clue about the "proper"
terminology and the code written back then is still working...

You're not the only one. But, again, what's wrong with learning
something correct every once in a while, even if it's not highly
important for the practical solution of the problem at hand?

<snip>
Fortunately , c.l.c will never become a perfect ivory tower, or at
the very least as long as I continue to post here... ;-)

Then, why are you arguing on the ivory tower side? ;-)

Since I'm not, the only correct answer to this question is: Mu. ;-)

Regards
--
Irrwahn Grausewitz (ir*******@free net.de)
welcome to clc: http://www.ungerhu.com/jxh/clc.welcome.txt
clc faq-list : http://www.faqs.org/faqs/C-faq/faq/
clc OT guide : http://benpfaff.org/writings/clc/off-topic.html
Nov 14 '05 #229
Da*****@cern.ch (Dan Pop) wrote:
In <cr************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:
Julie <ju***@nospam.c om> wrote:
Irrwahn Grausewitz wrote:
Julie <ju***@nospam.c om> wrote:
>Irrwahn Grausewitz wrote:

<snip>
>> What would you call p and *p, respectively?
>>
>> int main(void)
>> {
>> int a = 1;
>> int *p = &a;
>> *p = 2;
>> return 0;
>> }
>
>I call 'p' a "pointer [to an int]" and '*p' "p dereferenced" or "a pointer [to
>an int] dereferenced".

So you think the term "variable" is applicable to neither p nor *p?

I'd call p a variable, but not *p.

I agree with you here.

How would you call *p, though? It has the semantics of a variable,
doesn't it?

But only to some degree, and only in this special case, where p
happens to point to an object created by declaration of a variable,
that coincidentally has the same type p is a pointer to. See also
Ioannis' reply <cc***********@ ulysses.noc.ntu a.gr>, with which I
wholeheartedly agree.

<snip>
--
Irrwahn Grausewitz (ir*******@free net.de)
welcome to clc: http://www.ungerhu.com/jxh/clc.welcome.txt
clc faq-list : http://www.faqs.org/faqs/C-faq/faq/
clc OT guide : http://benpfaff.org/writings/clc/off-topic.html
Nov 14 '05 #230

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