Reply to: Write Algorithm – interview question

[ratewhore]

shoulda just said 'send it to India'. Or would that make you a PM?

[Jabberwocky]

So which part of the BT NHS project are you working??? on?

That reminds me ...

8) we need a team of testers
9) an IT support group
10) A budget for a couple of nights out to build team moral
11) A guy to keep the newspapers in the bogs freshly stocked - AtW, are you free ?

[PerlOfWisdom]

Well here is the JabberContractor solution:

0) get the hardware, we need plenty of servers to cope with demand, two for the db, one for the application server, two for web servers (redundancy), a further db server for the data analysts to enter the times. Then we need two further boxes for development work.
1) We need a database to store the times, so buy and install Oracle
2) We shall use Java, so install the Java run time on all boxes.
3) Obviously there will be a fourth generation user interface, so install Apache and a content management system to store user pages + graphics.
4) Tomcat provides the servlet server to handle dynamic interaction.
5) Now we will use distributed objects to distribute the load, so install an application server with an EJB container.
6) Next we hire a team of Java contractors, a PM to manage them and a team of data analysts to enter the data.
7) We download the code off the internet, sit back and read a user manual for three months.

So which part of the BT NHS project are you working??? on?

[Jabberwocky]

Well here is the JabberContractor solution:

0) get the hardware, we need plenty of servers to cope with demand, two for the db, one for the application server, two for web servers (redundancy), a further db server for the data analysts to enter the times. Then we need two further boxes for development work.
1) We need a database to store the times, so buy and install Oracle
2) We shall use Java, so install the Java run time on all boxes.
3) Obviously there will be a fourth generation user interface, so install Apache and a content management system to store user pages + graphics.
4) Tomcat provides the servlet server to handle dynamic interaction.
5) Now we will use distributed objects to distribute the load, so install an application server with an EJB container.
6) Next we hire a team of Java contractors, a PM to manage them and a team of data analysts to enter the data.
7) We download the code off the internet, sit back and read a user manual for three months.

[tim123]

I got caught by an interview question like this once.

I thought that he wanted to see how neat an algorithm I could come up with.

He didn't, he was more interested in seeing whether I bothered to validate the parameters etc before using them, which of course I had taken as read in an interview question but would have done in the real world.

I was annoyed with being caught out (not that I actually wanted the job).

tim

[Rebecca Loos]

Also it depends what programming language we are talking about
In Oracle PL/SQL you can use the decode function and write it in a one liner with it

[BlasterBates]

Its beyond me why anyone would write a recursive algorithm especially
when you can write this as a one liner.

[Bovvered]

One golden rule of recursion:-

"Never use recursion"

Computers' resources are finite, recursion's appetite for resources isn't.

Shut up.


P.S. I'm not promoting recursion for the algorithm in discussion.
P.P.S. Developers who write off techniques in one sweeping comment are generally crap.

[Sysman]

Anyone notice the question has an error?

... perhaps that was the real point of the exercise.

Just my banking experience showing through :-)

[messiah]

also there was no mention of needing current time in the parameters only a start and end time.

or am I wrong .... should I wear the dunces cap ?

[Jabberwocky]

Christ, is it what they pay stupid money for working in Banks?

-------------------------------------------------------
8:01 - 9:00 20% [i.e each minute is 1/3 %]
9:01 - 10:00 40% [i.e each minute is 2/3 %]
10:01 - 11:00 30% [i.e each minute is 1/2 %]
11:01 - 12:00 10% [i.e each minute is 1/6 %]
-------------------------------------------------------

1) you need simple function - CalcTradingRatio that accepts the following arguements:

a) %-tage of trading in given period
b) period start time, ie 8:01
c) period end time, ie 9:00
d) current time: this can be
d1) INSIDE period - in this case you calculation and return fraction of parameter a)
d2) BEFORE period starts (ie smaller then b) - return 0
d3) AFTER period ends - return full value a)

2) macro function that calls 1) for all periods:

string sCurTime="8:55";
int iTradingDone=0;

iTradingDone+=CalcTradingRatio("20","8:01","9:00", sCurTime);
iTradingDone+=CalcTradingRatio("40","9:01","10:00" ,sCurTime);
iTradingDone+=CalcTradingRatio("30","10:01","11:00 ",sCurTime);
iTradingDone+=CalcTradingRatio("10","11:01","12:00 ",sCurTime);

I wouldn't hire you mr atw - pass your parameters in using the correct type - percentages are floats, times should be typed too - what if the caller assumes a 24 hour clock - also I don't like iTradingDone as an int - what about rounding errors on each call - gosh the things I have to teach you people on here.

JabberNerd

[AtW]

AtW, I agree your solution is more elegant than mine

I actually would not be suprised if they accepted your solution rather than mine...

IMO there is too big emphasis onto how this simple problem is to be solved - they should be giving some real hard problems where solving the problem is important, not whether you use external function or not.

Perhaps the real answer they were looking for was that you will just outsource coding to people on Rent-A-Coder.

[DimPrawn]

Can I provide a solution by dragging pretty coloured icons onto a designer surface and then have a cup of tea?

[Rebecca Loos]

AtW, I agree your solution is more elegant than mine

But I wrote it in one single block on the grounds that the bank rejected a solution with an external function call

[Singleton]

Christ, is it what they pay stupid money for working in Banks?

-------------------------------------------------------
8:01 - 9:00 20% [i.e each minute is 1/3 %]
9:01 - 10:00 40% [i.e each minute is 2/3 %]
10:01 - 11:00 30% [i.e each minute is 1/2 %]
11:01 - 12:00 10% [i.e each minute is 1/6 %]
-------------------------------------------------------

1) you need simple function - CalcTradingRatio that accepts the following arguements:

a) %-tage of trading in given period
b) period start time, ie 8:01
c) period end time, ie 9:00
d) current time: this can be
d1) INSIDE period - in this case you calculation and return fraction of parameter a)
d2) BEFORE period starts (ie smaller then b) - return 0
d3) AFTER period ends - return full value a)

2) macro function that calls 1) for all periods:

string sCurTime="8:55";
int iTradingDone=0;

iTradingDone+=CalcTradingRatio("20","8:01","9:00", sCurTime);
iTradingDone+=CalcTradingRatio("40","9:01","10:00" ,sCurTime);
iTradingDone+=CalcTradingRatio("30","10:01","11:00 ",sCurTime);
iTradingDone+=CalcTradingRatio("10","11:01","12:00 ",sCurTime);

--

There done - pretty simple.

A faster way however is to split all periods into minutes and calculate cumulative trading done up to any given minute - put it all into array, then in order to calculate trading done in any given time you just calculate number of minutes from 8:00am and just look up trading value in array - this is very fast as pre-computation is needed only once.

Can't see ANY need for recursion here.

Sorry, I didn't get that one .. lets say start time is 8:15 and end time is 10:50 tell me how your solution works?