A question: Is 200,000 element array worth sorting and search?

[mike-yue]

The topic comes from a question:

Would you rather wait for the results of a quicksort, a linear search,
or a bubble sort on a 200000 element array?
1Quicksort
2Linear Search
3Bubble Sort

The answer is 2Linear Search

Could someone explain why Linear Search, not the other two options?
Or I misunderstood the original question?

Thanks you guys!

[James Harris]

On 4 May, 23:27, mike-yue <needpass...@gm ail.comwrote:

The topic comes from a question:

Would you rather wait for the results of a quicksort, a linear search,
or a bubble sort on a 200000 element array?
1Quicksort
2Linear Search
3Bubble Sort

The answer is 2Linear Search

Could someone explain why Linear Search, not the other two options?

Well, it's a poor question: asking what /you/ would prefer to do; but
presuming you want to wait as little time as possible wouldn't option
2 finish soonest? The fact that sorting and searching accomplish
different things also seems to be there to confuse.

You might be better asking questions on programming (i.e. not on C) in
comp.programmin g.

--

[Richard Heathfield]

mike-yue said:

The topic comes from a question:

Would you rather wait for the results of a quicksort, a linear search,
or a bubble sort on a 200000 element array?
1Quicksort
2Linear Search
3Bubble Sort

The answer is 2Linear Search

Could someone explain why Linear Search, not the other two options?
Or I misunderstood the original question?

The question is testing your knowledge of algorithmic complexity.

As the number of data items rises (especially past the limit where you can
reasonably think of all numbers as being basically the same size), you can
begin to ignore minor factors like the cost of overheads (e.g. opening a
file) and even, to some extent, the machine speed! All that matters, for
large N, is how this N affects the algorithm.

Quicksort is O(N * log N). Linear search is O(N). Bubble sort is O(N * N).

To understand, plot the graphs.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Peter Nilsson]

mike-yue wrote:

The topic comes from a question:

Would you rather wait for the results of a quicksort, a linear
search, or a bubble sort on a 200000 element array?
1Quicksort
2Linear Search
3Bubble Sort

The answer is 2Linear Search

Could someone explain why Linear Search, not the other two options?
Or I misunderstood the original question?

Given that 1 and 3 are sorts, and 2 is a search, and given that it's
far from clear what 'result' you're supposedly waiting for, I'd say
you have misunderstood, or you've mis-remembered it.

In any case, this is a general programming question, not a question
on the C language.

--
Peter

[mike-yue]

All very good answers. many thanks for you guys,
In a word, the Liner Search is the cheapest method to search. the
other two are complicated and expensive.

I know it is about algorithmic complexity, but I totally forget the
defination of the O, even the Log. University time seems a century ago
I almost forget everything.

I think it is useless for 99% programmer jobs, unfortunately it's
always been asked. Once a interviewer asked me to explain the
algorithmic complexity of quick sort!
Thanks again

[Richard Heathfield]

mike-yue said:

All very good answers. many thanks for you guys,
In a word, the Liner Search is the cheapest method to search. the
other two are complicated and expensive.

Whilst your claim is true, it is meaningless. Linear search is a search
technique. The other two are sorting techniques. It's tempting to say that
you're comparing apples with oranges, but it's more like comparing apples
with October.

I know it is about algorithmic complexity, but I totally forget the
defination of the O, even the Log. University time seems a century ago
I almost forget everything.

I think it is useless for 99% programmer jobs,

That's only true because 99% of programming jobs don't actually require
very much programming skill.

unfortunately it's
always been asked. Once a interviewer asked me to explain the
algorithmic complexity of quick sort!

Well, that's a reasonable question, isn't it? And hardly difficult.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Keith Thompson]

mike-yue <ne*********@gm ail.comwrites:

All very good answers. many thanks for you guys,
In a word, the Liner Search is the cheapest method to search. the
other two are complicated and expensive.

Please quote some context when you post a followup.

The missing context is the question in your original article:

| Would you rather wait for the results of a quicksort, a linear search,
| or a bubble sort on a 200000 element array?
| 1Quicksort
| 2Linear Search
| 3Bubble Sort

but neither Quicksort nor Bubblesort is a searching algorithm. Since
they do entirely different things, asking which one you'd rather wait
for doesn't make a whole lot of sense.

I know it is about algorithmic complexity, but I totally forget the
defination of the O, even the Log. University time seems a century ago
I almost forget everything.

I think it is useless for 99% programmer jobs, unfortunately it's
always been asked. Once a interviewer asked me to explain the
algorithmic complexity of quick sort!

And this was a problem? That's certainly something I'd expect any
good programmer to know. If you're going to be writing code that does
sorting and searching, and you don't know this stuff, there's an
excellent chance your code is going to be unacceptable slow.

(Quicksort is O(N log N) best case and average case; a straightforward
implementation is O(N**2) worst case, but it can be made O(N log N)
with a little tweaking.)

--
Keith Thompson (The_Other_Keit h) <ks***@mib.or g>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Charlton Wilbur]

>>>>"my" == mike-yue <ne*********@gm ail.comwrites:

myThe topic comes from a question: Would you rather wait for the
myresults of a quicksort, a linear search, or a bubble sort on a
my200000 element array?

I myself would rather wait for the results of a bubble sort; this
means I have much more chance of my tea being ready before the result
set is.

Charlton

--
Charlton Wilbur
cw*****@chromat ico.net

[Ian Collins]

Richard Heathfield wrote:

mike-yue said:

>All very good answers. many thanks for you guys,
In a word, the Liner Search is the cheapest method to search. the
other two are complicated and expensive.

Whilst your claim is true, it is meaningless. Linear search is a search
technique. The other two are sorting techniques. It's tempting to say that
you're comparing apples with oranges, but it's more like comparing apples
with October.

>I know it is about algorithmic complexity, but I totally forget the
defination of the O, even the Log. University time seems a century ago
I almost forget everything.

I think it is useless for 99% programmer jobs,

That's only true because 99% of programming jobs don't actually require
very much programming skill.

Or in my case, 99% of programming has been making hardware or web pages
tick, without a bit O in sight!

--
Ian Collins.

[CBFalconer]

mike-yue wrote:

>
The topic comes from a question:

Would you rather wait for the results of a quicksort, a linear
search, or a bubble sort on a 200000 element array?
1Quicksort
2Linear Search
3Bubble Sort

The answer is 2Linear Search

Could someone explain why Linear Search, not the other two
options? Or I misunderstood the original question?

It's a poor question. Quicksort is O(nLOGn), Linear search is
O(n), and bubble sort is O(n*n), where n is the size of the array,
here 200000. However linear searching doesn't require sorting, it
only requires examining each member of the original array for
equality. Since you get the linear answer quickest, and don't need
the array sorted, that is the optimum answer. The code is also the
simplest:

for (i = 0; i <= 200000; i++) {
if (a[i] == item) break;
}
if ((i <= 200000) && (a[i] == item)) return i;
else /* failure */ return -1;

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
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