comp.lang.c++ Google Group

Re: Math/CompSci Interview Question - Thoughts?

&nore...@axelvogt.de (Axel Vogt) — Sat, 21 Nov 2009 22:07:31 UT

<snipped>
Being a bit stupid I first would ask "Why? What do you do with it?"
and then I would pick on random. I am almost certain, that even at
a low number of draws the chance to get the very integer is higher
than implementing an algo without coding errors.

Re: Math/CompSci Interview Question - Thoughts?

al...@start.no (Alf P. Steinbach) — Sat, 21 Nov 2009 21:53:29 UT

* Bill Dubuque:
Hiya. Could you please explain the above more optimal solution. I'm unfamiliar
with the notation and not from a top-tier school, but in my experience anything
that's not nonsense can be visualized or explained in simple terms (e.g., Albert
Einstein did that beautifully with his book on special relativity, which except

Re: Math/CompSci Interview Question - Thoughts?

w...@nestle.csail.mit.edu (Bill Dubuque) — Sat, 21 Nov 2009 21:33:03 UT

I disagree. Saying that it's a puzzle rather than a programming problem
seems to imply that the solution is ad-hoc, rather than a special case
of some more universal technique. But that is not true here. Namely,
the proposed solution follows immediately from the obvious fact that
majority elts on product sets are preserved by component projections.

Re: How to get an insertion hint for an unordered associated container?

amrollahi.sa...@gmail.com (Saeed Amrollahi) — Sat, 21 Nov 2009 21:16:53 UT

On Nov 21, 10:34 pm, Pavel
Hi Pavel
AFAIK, the Unordered associative containers provide an ability for
fast retrieval
of data based on keys. As you know an - ordered - map is designed and
implemented
using Binary tree, so the complexity of retriving data is O(log n). In
the case of
unordered map, because it uses some hashing function, no comparision

How to get an insertion hint for an unordered associated container?

pauldontspamt...@removeyourself.dontspam.yahoo (Pavel) — Sat, 21 Nov 2009 19:34:15 UT

I am trying to figure out if I can use tr1/C++0x std::unordered_map to
speed-up an algorithm I did before using an ordered map.
The problem is quite common:
BEGIN
Given a key 'k', if no equivalent of 'k' is on the container, create
value and insert it; otherwise, update part of the value that is already

Re: Article on possible improvements to C++

pauldontspamt...@removeyourself.dontspam.yahoo (Pavel) — Sat, 21 Nov 2009 19:02:03 UT

It's of no use if the client code wants to know about the failure in few
higher-level callers. Of course you can create a class for every
overloaded + operator that can overflow, create a method "onOverflow()"
in it etc. but what level of cooperation would it require from the
client code to add and remove interested parties?

Re: Math/CompSci Interview Question - Thoughts?

mcdowe...@nospam.co.uk (A.G.McDowell) — Sat, 21 Nov 2009 18:46:21 UT

In article <6a8340b8-19b0-4fda-96d5-e744a ead1...@m26g2000yqb.googlegrou p
s.com>, Andrew Tomazos <and...@tomazos.com> writes
This sort of problem is covered by articles on Data Stream Processing in
CACM Oct 2009. (CACM is a lot more interesting these days than it was
some years ago). There are some very neat ideas in there, of which the

Re: Math/CompSci Interview Question - Thoughts?

c...@tiac.net (Richard Harter) — Sat, 21 Nov 2009 18:33:38 UT

On Sat, 21 Nov 2009 08:12:53 -0800 (PST), Andrew Tomazos
[snip code]
I hope "masters-equivilant" isn't on your resume.

Probably not, but that is not necessarily a good thing.
That's an interesting question with an interesting
presupposition. The first thing to understand is that this is a
puzzle rather than a programming problem. The presupposition is

Re: Why do some code bases don't use exceptions?

wo...@freemail.hu (White Wolf) — Sat, 21 Nov 2009 17:46:55 UT

I was referring to an "unprecedented amount". I mean if we disregard
the known trolls. I do not regard the OP as a troll, so it made me very
sad to see so many bad assumptions.

Re: Defining hash-keys?

al...@start.no (Alf P. Steinbach) — Sat, 21 Nov 2009 17:34:39 UT

* James Kanze:
It depends. Like how exactly the hash table handles collisions (search for next
available, overflow list, what?), and whether values tend to be bundled in small
intervals. I think doing the randomization thing is safest, but considering how
it might lead to excessive paging I'm not even sure about that -- depends also

Re: Math/CompSci Interview Question - Thoughts?

gwo...@figipc78.tu-graz.ac.at (GJ Woeginger) — Sat, 21 Nov 2009 17:29:14 UT

There is an old analysis of this problem by Fischer and Salzberg.
M.J. Fisher and S.L. Salzberg (1982)
Finding a majority among n votes.
Journal of Algorithms 3, pp 143-152.
If 2k elements contain a majority element (= an element that occurs at
least k+1 times), then you can find it with 3k-2 element comparisons

Re: Math/CompSci Interview Question - Thoughts?

p...@informatimago.com (Pascal J. Bourguignon) — Sat, 21 Nov 2009 17:24:10 UT

If what you're asking is whether anybody having a master in CS and
maths would have been able to come up with this solution in the
interview time, I guess we can answer that definitely no, otherwise
there would be no point in trying to select candidates with this test.
Obviously, it's because some people (with or without a master diploma,

Re: Why do some code bases don't use exceptions?

james.ka...@gmail.com (James Kanze) — Sat, 21 Nov 2009 16:50:02 UT

Just a linguistic nit, but formally, "unprecedented" means that
there is no precedent---no one has done it before. Given this
definition, I wouldn't call posting a web page on a subject you
know nothing about exactly "unprecedented":-).
Not that that that changes anything with regards to your
argument.

Re: Why do some code bases don't use exceptions?

james.ka...@gmail.com (James Kanze) — Sat, 21 Nov 2009 16:45:48 UT

What is the perceived problem? And why is aborting (as a
default behavior) a bad solution? Violating an exception
specification is a contract violation, so aborting *is* about
the only appropriate default behavior. The question is: what
problem is solved by supporting contracts in which a function

Re: Defining hash-keys?

james.ka...@gmail.com (James Kanze) — Sat, 21 Nov 2009 16:34:43 UT

std::map will take an std::vector<int> as a key. No need to
convert to string. (The access will still be O(lg n), rather
than O(1), but that's often enough.)