ZIO 2017 Discussion

mathecodician · November 20, 2016, 9:14pm

In Delhi there were about 400 students but the location and the ambience was very bad.

siddharth2000 · November 20, 2016, 9:14pm

No i mean the explanation of question 10 11 12

siddharth2000 · November 20, 2016, 9:17pm

Btw i was getting 595 in q.6

siddharth2000 · November 20, 2016, 9:23pm

Plz post the questions as well if possible

sandy999 · November 20, 2016, 9:25pm

@siddharth2000 Oh sorry.

My approach wasn’t very elegant.

There are 3 stages, to find all possible ways to select substring

0011
00110011
001100110011

For 1) I calculated at each position of the binary string, the no. of 0011 ending at that index. Then added the values at each index

For 2) In addition to what I did for 1), I calculated at each position of the binary string, the no. of 0011 starting at that index.

Now, at each index, multiplied no. of 0011 ending at that index, and no. of 0011 starting at the next index. Added up.

For 3), not too clear to put it in black and white, since the test cases could have been more complicated,

Find the index at which the first 0011 ends.

Find the index at which the last 0011 starts.

Now look at the middle elements, see how many 0011 you can get. This is your answer for stage 3.

Let me know if there’s any flaw. I also most likely made careless calculation mistakes while doing the above.

saioneer3683 · November 20, 2016, 9:31pm

Hey the ones who had problems during ZCO/ZIO should mail it to the authorities… I am in class 11 and am expecting 40-50.
Q4 to Q 10 were the easiest and the correct answers were posted. For Q1 to Q3, I messed up. For the last answer I too got 21, Something I do not remember, and something in 100s. I’d say the cut off should be around 40 for 10 and below, 45 for 11, and 50 for 12. Good Luck
P.S. Pls post your expected marks, class and what you felt should be the cut-off.

saioneer3683 · November 20, 2016, 9:31pm

Hey the ones who had problems during ZCO/ZIO should mail it to the authorities… I am in class 11 and am expecting 40-50.
Q4 to Q 10 were the easiest and the correct answers were posted. For Q1 to Q3, I messed up. For the last answer I too got 21, Something I do not remember, and something in 100s. I’d say the cut off should be around 40 for 10 and below, 45 for 11, and 50 for 12. Good Luck
P.S. Pls post your expected marks, class and what you felt should be the cut-off.

siddharth2000 · November 20, 2016, 9:34pm

I think i might have misinterpreted the last 3 questions as for question 10 my answer was 81 instead of 21.

sandy999 · November 20, 2016, 9:39pm

Could you please post your solution to the 4th problem? It would help to know better approaches

tantheta · November 20, 2016, 9:49pm

Guys my 8 out of 12 questions are correct… i.e. 50 out of 80… will i qualify…??
The cutoff of the previous years was less than 50… so…??

shlok_1933 · November 20, 2016, 10:15pm

Hey, i’m a class 8th student too.
I took part in ZCO and i think i will score around 50 marks.
will i be able to qualify?

P.S. when are the results coming?

animesh_f · November 20, 2016, 11:16pm

The answers for the last question should be something like 21, 144, 154.

The expected solution was using dynamic programming :

dp[i][0] denotes number of subsequences in the first (i) indices of the string that end with “0”

dp[i][1] denotes the same for “00”

dp[i][2] denotes the same for “001”

dp[i][3] denotes the same for “0011”

What we seek is just dp[stringLength][3]


(http://pastie.org/pastes/10966296/text?key=zzyanb8jua9cfjomrklrq)

mathecodician · November 20, 2016, 11:25pm

I literally did the ditto same thing by making a dp matrice.
But because of some calculation mistake, I got the second part wrong.

animesh_f · November 20, 2016, 11:36pm

Ah, that’s ok. You did exceptionally well, especially considering that you’re an 8th grader.

dr_seuss · November 21, 2016, 12:30am

Paper was significantly easier than usual this year. Cutoff should be around 50 for 12 in my opinion.

dr_seuss · November 21, 2016, 12:48am

How is everyone getting a larger answer for 4c than for 4b??

Even though the 4c binary string is longer than the 4b one, there are some bits in 4c which cannot appear in any good number. I can’t remember the exact strings, but for instance, the second bit in the 4c string was a 1 which has to be dropped for all possible good numbers since there must be at least two zeroes before a 1 in a good number and it is impossible to have two zeroes before the second position. Similarly, the zeroes at the end of the 4c string must also be dropped since they cannot be followed by a 1. Such reductions make the 4c string a sub string of the similarly reduced 4b string. (Do I make sense?)

I can’t remember my 11 & 12 answers because I changed them at the last minute, realizing I had been undercounting. But I’m relatively confident of this much; so I’m surprised that everyone seems to have larger 4c answers than 4b ones.

saioneer3683 · November 21, 2016, 6:47am

Did anyone else face problems with the interface during ZIO?

sreycodes · November 21, 2016, 6:48am

All of you are getting answer for question 2 part 2 as 10, but I think it is 9. Based on my memory I remember the values were
1-6
2-7
3-7
4-8
5-8
6-9
And a few more with 9.
So if 1 seeks for 3 rounds, 2 and 3 seek for 2 rounds each and 4 and 5 seek for one round each, I think every one will be satisfied.
Please point out if I have made a mistake.
All the best to everyone for results !

kiran27 · November 21, 2016, 7:07am

For Ques 6 is the answer 593 or 599.
I see both answers, Can someone confirm?

siddharth2000 · November 21, 2016, 9:18am

anyone remember testcases of 1st question or atleast the example. plz post them if u do remember