# Delete every mth element in a linked list ??

Discussion in 'C Programming' started by Aditya, Dec 20, 2006.

This is a normal interview question, which goes like this
"Given a linked list of integers, delete every mth node and return the
last remaining node."

Delete every 3rd node (m = 3) and return the last remaining node
meaning...
4->6->3->5->10->1->17
4->3->5->1->17
3->5->17
3->17
3

after deleting every 3rd node the last remaining node is 3, so node
with data 3 is returned.
function prototype:

{

}

thanks
A

2. ### Richard HeathfieldGuest

> This is a normal interview question, which goes like this
> "Given a linked list of integers, delete every mth node and return the
> last remaining node."
>
> eg: Linked list = 4->6->7->3->5->6->10->1->23->17
> Delete every 3rd node (m = 3) and return the last remaining node
> meaning...
> 4->6->3->5->10->1->17
> 4->3->5->1->17
> 3->5->17
> 3->17
> 3
>
> after deleting every 3rd node the last remaining node is 3, so node
> with data 3 is returned.
> function prototype:
>
> node* deleteEveryMth(node** head, int m)
> {

No, yours.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

Richard Heathfield, Dec 20, 2006

3. ### Ian CollinsGuest

> This is a normal interview question, which goes like this
> "Given a linked list of integers, delete every mth node and return the
> last remaining node."
>

Please don't post to multiple groups, cross post if you must, or better
still, post to one group.

--
Ian Collins.

Ian Collins, Dec 20, 2006
4. ### jaysomeGuest

On 20 Dec 2006 01:36:00 -0800, "Aditya" <> wrote:

>This is a normal interview question, which goes like this

I've never asked this question in an interview, nor do I ever plan to.
I guess I must be abnormal.

>"Given a linked list of integers, delete every mth node and return the
>last remaining node."
>
>Delete every 3rd node (m = 3) and return the last remaining node
>meaning...
>4->6->3->5->10->1->17
>4->3->5->1->17
>3->5->17
>3->17
>3
>
>after deleting every 3rd node the last remaining node is 3, so node
>with data 3 is returned.
>function prototype:
>
>{
>
>}

I have no clue.

But if, and when, I ever need to know how to delete every mth node in
a linked list of integers, I'll spend the time to learn how to do it
right, and I'll get it right. And the customer will pay me dearly for
it.

At an interview, I start off with asking very simple questions, like
what's wrong with the following statements?

void main(void);
i = i++ % MAX_VAL;
p = (int*)malloc(4 * 4);
int main(void) {return -1;}
goto ERROR;
gets(s);
fflush(STDIN);
#define N X+1
unsigned i; for(i=1;i>=0;i--)
while(1)

Once they answer those questions, it's usually easy to determine where

--
jay

jaysome, Dec 20, 2006
5. ### Richard HeathfieldGuest

jaysome said:

<snip>
>
> At an interview, I start off with asking very simple questions,

Ooh, ooh, I love these...

> like
> what's wrong with the following statements?
>
> void main(void);

It's not a statement.

> i = i++ % MAX_VAL;

MAX_VAL is undefined, so you can't take its percentage.

> p = (int*)malloc(4 * 4);

(int*): malloc returns a pointer, and you can't multiply ints by pointers.

> int main(void) {return -1;}

The actual program has been left out.

> goto ERROR;

goto can't be an error; it's a keyword, so it's built into the language.

> gets(s);

Should be: s = gets(s);

> fflush(STDIN);

Ah, good old case sensitivity. This should of course be FFLUSH(STDIN);

> #define N X+1

As everyone knows, X stands for unknown, so X+1 is meaningless.

> unsigned i; for(i=1;i>=0;i--)

i is a lousy name for a variable. Better:

unsigned eternity_ring; for(eternity_ring = 1;
eternity_ring >= 0;
eternity_ring --)

Note the cool formatting, which should ensure that I get 11/10 for this
quiz.

> while(1)

Should be while(2), as it is the second loop in this test.

> Once they answer those questions, it's usually easy to determine where

How did I do?

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

Richard Heathfield, Dec 20, 2006
6. ### Mark L PappinGuest

Richard Heathfield <> writes:

> jaysome said:
>> At an interview, I start off with asking very simple questions,

....
>> Once they answer those questions, it's usually easy to determine
>> where the interview is headed.

>
> How did I do?

mlp

Mark L Pappin, Dec 20, 2006
7. ### BarryGuest

news:...
> This is a normal interview question, which goes like this
> "Given a linked list of integers, delete every mth node and return the
> last remaining node."
>
> eg: Linked list = 4->6->7->3->5->6->10->1->23->17
> Delete every 3rd node (m = 3) and return the last remaining node
> meaning...
> 4->6->3->5->10->1->17
> 4->3->5->1->17
> 3->5->17
> 3->17
> 3
>
> after deleting every 3rd node the last remaining node is 3, so node
> with data 3 is returned.
> function prototype:
>
> node* deleteEveryMth(node** head, int m)
> {
>
> }
>
> thanks
> A
>

The example looks broken. And how do you delete the 3rd node
from a list with two entries?

Barry, Dec 20, 2006
8. ### BarryGuest

"Richard Heathfield" <> wrote in message
news:...
> jaysome said:
>
> <snip>
> >
> > At an interview, I start off with asking very simple questions,

>
> Ooh, ooh, I love these...
> > unsigned i; for(i=1;i>=0;i--)

>
> i is a lousy name for a variable. Better:
>
> unsigned eternity_ring; for(eternity_ring = 1;
> eternity_ring >= 0;
> eternity_ring --)
>
> Note the cool formatting, which should ensure that I get 11/10 for this
> quiz.
>
> > while(1)

>
> Should be while(2), as it is the second loop in this test.
>

I would have missed this one I would have said it should be:
unsigned i; for(i=1;i>=0;i--)

Barry, Dec 20, 2006
9. ### Richard HeathfieldGuest

Barry said:

<snip>

> The example looks broken. And how do you delete the 3rd node
> from a list with two entries?

Like this.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

Richard Heathfield, Dec 20, 2006
10. ### Random832Guest

2006-12-20 <>,
jaysome wrote:
> void main(void);

Nothing, assuming that main is never used in the scope in which this
declaration appears.

> p = (int*)malloc(4 * 4);

There's several things wrong with it. The most obvious one is casting
malloc, but there's also the assumption that int has a size of 4.

> int main(void) {return -1;}

The range of values that main may return is implementation-defined. On
some implementations (this answer is appropriate if interviewing for
a position where you know you'll be programming for windows or unix), it
must be between 0 and 255. For portable code, it must be 0,
EXIT_SUCCESS, or EXIT_FAILURE.

> goto ERROR;

ERROR is a reserved identifier. (I hope this is what you were looking
for, rather than some trite condemnation of the use of "goto" without
seeing the context)

> fflush(STDIN);

Nothing, assuming that STDIN is of type FILE * and points to a file
opened for output. However, isn't that a bit of a trick question? It'd
be bad programming practice to use that name anyway I guess.

> unsigned i; for(i=1;i>=0;i--)

i will wrap around to at least 65535 after reaching 0; it will never
become less than 0.

> while(1)

Not sure I see the problem here. for(; might be better style.

If you think it's less efficient, this says more about the interviewer
than the interviewee.

> Once they answer those questions, it's usually easy to determine where

Random832, Dec 20, 2006
11. ### jaysomeGuest

On Wed, 20 Dec 2006 10:42:51 +0000, Richard Heathfield
<> wrote:

>jaysome said:
>
><snip>
>>
>> At an interview, I start off with asking very simple questions,

>
>Ooh, ooh, I love these...
>
>> like
>> what's wrong with the following statements?
>>
>> void main(void);

>
>It's not a statement.
>
>> i = i++ % MAX_VAL;

>
>MAX_VAL is undefined, so you can't take its percentage.
>
>> p = (int*)malloc(4 * 4);

>
>(int*): malloc returns a pointer, and you can't multiply ints by pointers.
>
>> int main(void) {return -1;}

>
>The actual program has been left out.
>
>> goto ERROR;

>
>goto can't be an error; it's a keyword, so it's built into the language.
>
>> gets(s);

>
>Should be: s = gets(s);
>
>> fflush(STDIN);

>
>Ah, good old case sensitivity. This should of course be FFLUSH(STDIN);
>
>> #define N X+1

>
>As everyone knows, X stands for unknown, so X+1 is meaningless.
>
>> unsigned i; for(i=1;i>=0;i--)

>
>i is a lousy name for a variable. Better:
>
> unsigned eternity_ring; for(eternity_ring = 1;
> eternity_ring >= 0;
> eternity_ring --)
>
>Note the cool formatting, which should ensure that I get 11/10 for this
>quiz.
>
>> while(1)

>
>Should be while(2), as it is the second loop in this test.
>
>> Once they answer those questions, it's usually easy to determine where

>
>How did I do?

Further interrogation would be required to determine that. I must
moment while I grabbed my Schildt hard-copy of the standard. I'd
recite a good number of carefully chosen passages from the text of the
book, and simply ask you after each citation: "Am I reading from the
left or the right page"? Answer them all and you'd score an 11.

Happy Holidays
--
jay

jaysome, Dec 21, 2006
12. ### Richard HeathfieldGuest

jaysome said:

> On Wed, 20 Dec 2006 10:42:51 +0000, Richard Heathfield
> <> wrote:

<snip>

>>How did I do?

>
> Further interrogation would be required to determine that. I must
> moment while I grabbed my Schildt hard-copy of the standard. I'd
> recite a good number of carefully chosen passages from the text of the
> book, and simply ask you after each citation: "Am I reading from the
> left or the right page"? Answer them all and you'd score an 11.

Easy-peasy. "Yes. Yes. Yes." (Watching interviewer's eyes carefully...) "No,
you just made that one up. Yes. Yes. No. ..."

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

Richard Heathfield, Dec 21, 2006