ZIO 2015 Discussion

@superty I tried reading your answer, but my notation and method was far different … basically brute force.

Will an answer key be released? And is it true that the cut-off is 30 for class 11th students?

You’re right. I saw a flaw in my answer…
I assumed that the sequence EEEELLLLEELL is an illegal sequence but as it turns out my answer is incomplete

So How many marks is everybody getting ? Mention your marks and class in the comments.
50 marks 12th grade

No reputation == No comments
Also I am class 12 and marks are 40 (two epic mistakes in one sub part each of Q1 and Q3 + total downfall in Q2).

@Organic-Shilling No comments for me too - Class 11th, 70 marks (got 4c wrong)

Class 10th. 50 Marks.

Yes but I am a little weak in algorithms

@Organic-Shilling

Q2)

your answer for part b and c are correct (even I got the same)
but for part (a) i got 96

given n=6 & k=8 (Ti denotes train i, E-enter, L-leave)

first T1 enters(obviously)
now since k=8 we can have maximum of 4 more trains entering and leaving before T1 leaves

case 1:

4 trains(T2 to T5) enter and leave before T1 leaves,that is, fix the position of T1 as 5 in the output sequence:
there are 14 possible ways in which T2 to T5 occupy the first 4 positions in the output sequence(can be easily verified)

For each of these 14 ways,there is only 1 way in which T6 can occupy the sixth position(EL)

So, 14 x 1 = 14;

case 2:

3 trains(T2 to T4) enter and leave before T1 leaves,that is, fix the position of T1 as 4 in the output sequence:

there are 5 possible ways in which T2 to T4 occupy the first 3 positions in the output sequence(can be easily verified)

For each of these 5 ways,there are 2 ways in which T5 & T6 can occupy the 5th and 6th position(EELL and ELEL)

So, 5 x 2 = 10;

case 3:

2 trains(T2 , T3) enter and leave before T1 leaves,that is, fix the position of T1 as 3 in the output sequence:

there are 2 possible ways in which T2 & T3 occupy the first 2 positions in the output sequence

For each of these 2 ways,there are 5 ways in which T4 to T6 can occupy the last 3 positions.
So, 2 x 5 = 10;

case 4:

1 train(T2) enter and leave before T1 leaves,that is, fix the position of T1 as 2 in the output sequence:
there is only one possible way in which T2 occupies the first position in the output sequence
For this one way,there are 14 ways in which T3 to T6 can occupy the last 4 positions.

So, 1 x 14 = 14;

So far total output sequences generated: 14+10+10+14=48;

case 5:

zero trains enter and before T1 leaves,that is, fix the position of T1 as 1 in the output sequence:
now again we have 5 more trains(T2 to T6) which have 48 output sequences as shown above.

hence total no. of output sequences = 48x2 = 96;

ANS:96

I am getting 50. Grade 10. Can i be selected with this much . made a silly mistake , else would have got 60

@a1a99_3

The answer for case 5 is 42, not 48. The sum of previous cases is not equal to the last case, it needs to be calculated separately.

@adityakhanna1999

It is unlikely that cutoff for 10th will be more than 40.

@superty

for case 5

now you have T2 to T6 instead of T1 to T5 and rest is the same

even though u calculate separately u will again repeat cases 1 to 4 and hence the count is 48 only.

What is expected cut off for class 11?
Last year in class 10 my score was 40 and class 10 cut off was 25 and 11 cut off was 30.
This year my score is 35

@a1a99_3

It is not the same. Cases 1-4 calculate for T1 to T6, not T1 to T5.

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I got the exact same answers as you! I’m in class 9 BTW…

I solved problems 1, 3 and 4 correctly (and completely)! I’m getting 60!!

Hi all!

I’m in 9th grade and I scored 60 in ZIO according to these answers.

I hope I get qualified for the NEXT LEVEL.

I am quite comfortable coding using Python and Javascript and am considerably proficient at HTML/CSS.

I have no experience in C, C++ and Pascal but I have very little experience doing with Java (or Oak as I think it should rightfully be called).

I’m planning to go ahead and use Java for INOI. In order to do so, I have to learn Java within the next 2 months.

I want to have enough expertise to be able to solve the INOI problems so um… Does anybody have any suggestions as to how to learn Java? (I notice the redundancy)

@data2000

I second Organic-Shilling, most people use C++ so it’ll be easier for you to ask for help as well, and it doesn’t make much of a difference right now since it’s not like you’ve already started with Java and you have to switch,

Also, note that you only need to know the basic topics listed here: http://www.iarcs.org.in/inoi/online-study-material/topics/

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Hey!
According to your solutions, I would get 50 Marks and I am in Class 11. Will I make it through? Anyway, Thanks for posting the answers and also for the discussions! If I pass the cut-off, what should be my preparations for the next level? I have been learning C++ in my school for this year. Would that be enough? Cause, I don’t even know what Brute-Force algorithm is! And I seriously think I am under prepared for this.

Btw, for the third part of the last question, I got it as 11. I don’t know how I got that wrong.

Hey friends , what do u think will be the cut off of this year in ZIO ? Does someone knows about cut offs of last few year?

DISCLAIMER: Claims made here about the cutoff are mere speculations and can’t be taken to be absolutely true. (NOTE: Wrote this disclaimer because I don’t want anyone to lose hope/get depressed/ask about cutoffs, however you may post your mistakes for other benefit) (By the way as you already know I get 40 in class 12 and a big ZERO in ZCO) ;-(

By what time today , the results are gonna be announced?