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# How did you solve the problems in today's paper ? What's the expected cutoff ?

 3 I saw an email today with subject, "INOI 2015 Evaluation". I lost a heartbeat. Then I realised that it was just a general email -_- answered 08 Feb '15, 21:03 6★ketanhwr 1.9k●3●18●44 accept rate: 15% Yeah, same. A better title would have been "Update on INOI 2015 Result Date" or something. (08 Feb '15, 21:08) superty3★ LOL SAME REACTION (08 Feb '15, 23:49) Heh, exactly; I thought they'd e-mailed me my scores. sigh (09 Feb '15, 16:30) idraumr0★ It's thursday already. When will they release the result? (12 Feb '15, 13:36) ketanhwr6★ Hopefully Friday, Saturday or Sunday. (12 Feb '15, 14:23) superty3★ Or next week. (12 Feb '15, 15:41) idraumr0★ Yeah, but hopefully this week. (12 Feb '15, 15:45) superty3★ showing 5 of 7 show all
 2 "[The cut-off is] Likely to be 100. Will have an announcement soon." answered 13 Feb '15, 16:29 0★idraumr 246●3 accept rate: 45% Good, good. (13 Feb '15, 18:10) superty3★ Nothing yet. (13 Feb '15, 20:24) nibnalin6★ Soon might be 2 days. (13 Feb '15, 20:26) superty3★ And how right we both were, @superty. :D (14 Feb '15, 13:10) idraumr0★ Well, I wasn't right, I was talking about the announcement, not the final result. Technically the announcement came today. (announcement of your score) (14 Feb '15, 13:32) superty3★ Ah, I meant the announcement of the final list. (14 Feb '15, 13:38) idraumr0★ When is the final result coming? (16 Feb '15, 13:19) ketanhwr6★ showing 5 of 7 show all
 1 Ok guys, as all of you would have seen your scores, and most of you finalised it, lets try to approximate the cutoff: Please choose your score: INOI score (vote only after you have finalised your score) answered 14 Feb '15, 19:39 21●3 accept rate: 0% I don't think we need this. The cut-off is most probably going to be 100. The result will be out tomorrow, anyway. (14 Feb '15, 19:55) idraumr0★ But still. Why not check it?! (14 Feb '15, 19:56) ketanhwr6★ @idraumr the result will be out on Monday. (14 Feb '15, 19:56) ketanhwr6★ D'oh. Sorry, totally thought tomorrow is Monday. I've voted, for what it's worth. (14 Feb '15, 19:58) idraumr0★ I know it is not at utmost necessity, but an estimate is definitely going to be good. We can also know the score distribution this year. (14 Feb '15, 20:01) http://strawpoll.me/3636949/r Omg, 10 people got 200!!!! And 19 people getting >100! So cutoff probably is 110 or so.... (17 Feb '15, 21:38) showing 5 of 6 show all
 0 Same here ,the second problem was a bit tricky. Felt a bit sad . :( . Could have done better. answered 31 Jan '15, 13:03 13●3 accept rate: 0% Ya, once I heard the logic, it felt but-obvious, but then, the past is past... (31 Jan '15, 13:17) nibnalin6★
 0 I did 1st one. It was a nice DP. First calculate the maximum sum possible for i less than j using Kadane's algorithm (had to modify it a bit). For i greater than j, precalculate the maximum sums possible and traverse the array one. Overall complexity O(n). Couldn't solve the 2nd problem completely. Solved first subtask using Inclusion Exclusion Principle. Since w = v^n. Therefore |w| = n|v| where |s| denotes the length of string s. So for n>=2, find all factors of |w| and use IEP to find all the possible periodic strings. Now in the end subtract this value from 2^n. Another answer: Here we will consider '1' as a prime number. Now the total periodic strings will be: 2^p1 + 2^p2 +... - 2x(k-1) where k are the number of prime factors of n (including 1 and excluding n). SO the answer will be 2^n - (2^p1 + 2^p2 + ... -2x(k-1)) answered 31 Jan '15, 13:25 6★ketanhwr 1.9k●3●18●44 accept rate: 15%
 0 As far as the cutoff is concerned ,I think it will be >=125, considering most of the students solving the first question correctly ,and the second question ..... duh .... say most with subtask 1 correct. Could have been selected , if had may be 1/2 hrs more ... but yeah .. past is past.. :( answered 31 Jan '15, 14:30 13●3 accept rate: 0% 1 Am I the only one who thought that 1 problem was harder than the second one ? (31 Jan '15, 14:52) 1 Nope. I thought the same. Problem 1 is definitely harder IMO. (31 Jan '15, 14:53) superty3★
 0 Did anyone feel that the sample testdata for Subtask 3 (and maybe 4 also) of Problem 2 was incorrect? I think one of them at least is easy to prove wrong. Input: 1260 99999989 Output: 3323612 (2^1260) mod 99999989 is 3007916. So their answer is more than 2^n, not possible. I know its mod, but there's no way that the amount you have to subtract is 99684293, that's way too large. Really crossing my fingers that those answers were wrong, I attempted only Problem 2! answered 31 Jan '15, 14:31 13●1●3 accept rate: 0% @sandy999 Yeah, that was more or less the way I did it, except I grouped the factors by prime numbers and took away all the strings of that length, not just non-periodic strings. (31 Jan '15, 14:41) 1 sorry but I don't think they are wrong at least my program gave correct answers on all the sample test data (31 Jan '15, 14:52) 1 Yeah I don't think they're wrong. (31 Jan '15, 14:53) superty3★ @vikramnitin9 If you take away all strings of that length, you'd end up taking away strings like 00...000 and 11...11 more than once! (31 Jan '15, 14:58) sandy9992★ Yeah, so subtract 2 after raising every prime factor except 1. Those are the only two repetitions, I think. Am I right? (31 Jan '15, 15:04) You're right I guess. Which anyway means that you're taking the non periodic strings only (I don't know why you said you're taking away all strings of that length), considering that 1 gives 2 non periodic strings. (31 Jan '15, 15:20) sandy9992★ Are you saying that the number of periodic strings of length 1260 is less than 10^8? There are 2^630 strings of length 630, and thus there are at least that many periodic strings of length 1260. (31 Jan '15, 15:27) superty3★ Just to clarify, as an example, what would be the correct approach if n=12? 12 = 1 x 4 x 3, so my approach would be (2^12)-((2^1) + (2^4 -2) + (2^3 -2)) So for 1260 = 1 x 4 x 9 x 5 x 7, I subtract (2^1)+(2^4 -2), etc I have a vague feeling that there's something wrong with this, though. (31 Jan '15, 15:27) It's correct, but the way I reached it is different: 2^12 - ((2^1) + (2^2 - 2^1) + (2^4 - (2^2 - 2^1) - 2^1) + (2^3 - 2^1)) (31 Jan '15, 15:35) superty3★ So are the two ways exactly equivalent? In your method, do you also include (2^6 -2) ? And @sandy999, I did that intentionally, to combine both in one step. Eg: I wanted to take away 1010 and 0101 also. These are patterns for 2, but they can be merged with 4. (31 Jan '15, 15:42) Yeah, didn't notice that. (31 Jan '15, 15:45) sandy9992★ I don't think so, I think they happen to be equivalent in this case. (31 Jan '15, 15:46) superty3★ My method must be wrong, because like you mentioned above, for 1260, I don't take 2^630, only its individual factors. (31 Jan '15, 15:47) Do you mean prime factors? If so, that's definitely wrong. If not, 630 is a factor of 1260. (31 Jan '15, 15:49) superty3★ I think I get what you mean. So you would include 2^6 as well in the 2^12 example, right? (31 Jan '15, 15:51) 2 Oh yeah you are right, I was wrong in that comment. Wow two people upvoted that lol. The answer is: 2^12 - ((2^1) + (2^2 - 2^1) + (2^4 - (2^2 - 2^1) - 2^1) + (2^3 - 2^1) + (2^6 - (2^3 - 2^1) - (2^2 - 2^1) + 2^1)) (31 Jan '15, 15:54) superty3★ showing 5 of 16 show all
 0 I'm surprised there wasn't a graph question, I was convinced that there was going to be one graph and one DP. answered 31 Jan '15, 15:12 3★superty 364●1●7 accept rate: 31% 1 Same! I wish there wasn't a departure from the pattern, but sigh. (31 Jan '15, 15:18) idraumr0★ last year was comparitively cakewalk. One question was direct Floyd warshall and the 1st question was difficult, but not impossible... (31 Jan '15, 15:49) nibnalin6★ The first question last year was, in my opinion, easier than both of the questions this year. It was definitely easier to qualify though, because the cutoff was only one question. (31 Jan '15, 15:52) superty3★ On the other hand, we've better programmers appearing this year... (31 Jan '15, 15:55) idraumr0★ I did take that into account, I still think it was harder last year. (31 Jan '15, 15:56) superty3★ according to me last year's first question was definitely harder then the second question this year and It totally depends on the person whether or not it was harder then the first question this year. last year's recurrence was easy where as coding part was difficult whereas it was opposite in this year's first problem (31 Jan '15, 16:08) @superty, today being the day I spend drowned in anxiety as to whether I'd qualify, I can only hope that's true and I qualify. :-) (31 Jan '15, 16:09) idraumr0★ I disagree that last year's recurrence was easy, I would argue that the recurrence was difficult but the implementation was easy. This year both were hard... oh. Yeah maybe this year was harder. One would expect it to get harder as time goes on anyways. (31 Jan '15, 16:16) superty3★ No Highwaybypass was a tad easier than both the problem s (31 Jan '15, 18:10) arpanb83★ Okay, maybe I undercompensated (31 Jan '15, 18:15) superty3★ 1 Heh; so last year, poor skills + poor questions = 100 cut-off. This year, good skills + good questions = (!). (31 Jan '15, 18:48) idraumr0★ 2 The average skill level increases only very slightly every year. Most of the people who did well last year aren't participating this year, and we won't be participating next year. The people who did badly this year will do better next year. The number of people doing well doesn't change much from year to year. (31 Jan '15, 18:53) superty3★ showing 5 of 12 show all
 0 I'm just wondering, do they actually check the code, or just judge with testcases? I came up with an algorithm for the second question, similar to @sandy999's but I was anxious about the O(N^2) complexity (and it was terribly slow, was taking more than 3 seconds for an n=150000 input, which was probably some flaw in my implementation, considering that it worked for some others), so I precomputed the number of non-periodic strings for all prime numbers till 387 and put them in a lookup table. I'm hoping precomputation doesn't count against my score, since the code was working fine for all sample cases. answered 31 Jan '15, 16:53 1★hackpert 1 accept rate: 0% 1 I don't think that's officially wrong (no rule says you can't pre-compute). You'll want to mail the organisers to be double-sure. It's still somewhat a "bad" way to solve the problem, given that you obviously did something wrong. (31 Jan '15, 16:56) idraumr0★
 0 Given that we've more or less a week to the results, does everyone want to participate in a quick collaboration to figure out the cut-off? Just simply note in a comment the number of people you think will score >= 100, including yourself. Please don't give answers with duplicates. I know of myself scoring (probably) 130. (A few more, but those are guessimates.) Cheers. answered 31 Jan '15, 17:16 0★idraumr 246●3 accept rate: 45% 1 I'm the only person I know of, so that makes 2 + the few people you know of getting ~160. (31 Jan '15, 17:18) superty3★
 0 Shagun , Parth of dps rkp and me would also be most probably scoring above or equal to 100. answered 04 Feb '15, 15:02 1●1 accept rate: 0%
 0 That brings us to 24. Shagun has been to IOITC last year. answered 04 Feb '15, 15:06 1●1 accept rate: 0%
 0 when can we expect the results? answered 05 Feb '15, 10:45 11●1●1 accept rate: 0% I was told within a week (from 31st Jan). (05 Feb '15, 11:51) idraumr0★ The result must be coming in a day or so. (06 Feb '15, 11:18) ketanhwr6★ It seems it's going to take a few more days. (06 Feb '15, 12:02) superty3★ Why? Did you ask them? They aren't replying to my mail. Last year, the result came in exactly 2 weeks. (06 Feb '15, 13:47) ketanhwr6★ @idraumr asked them. (06 Feb '15, 13:51) superty3★ Sigh; someone should figure out what takes them so long. (06 Feb '15, 14:01) idraumr0★ Waiting sucks. Ask them to tell your score if yours have been checked. (06 Feb '15, 14:13) ketanhwr6★ I don't think they would be willing to do that. Someone who's gone to camp in previous years might have a better idea of what's going on. (06 Feb '15, 14:19) superty3★ Yeah. Anyone? (06 Feb '15, 14:23) ketanhwr6★ I asked them my score, regardless. Let's see how they respond. Did you ask for the same, @ketanhwr? Although, yes, can someone who has more knowledge of how the process goes educate me as to why this takes an insane amount of time? (06 Feb '15, 14:51) idraumr0★ @idraumr no I didn't, but am planning to if the results don't come out by sunday. (06 Feb '15, 16:06) ketanhwr6★ Guys it's sunday today, anyone got any updates ? (08 Feb '15, 12:33) nibnalin6★ showing 5 of 12 show all
 0 Will the qualifiers be informed by e-mail( as they did in case of ZCO )? answered 06 Feb '15, 17:48 469●6●30 accept rate: 7% I presume so; how much are you expecting? (06 Feb '15, 17:54) idraumr0★
 0 Do they tell us the scores? answered 10 Feb '15, 14:57 3★data2000 1●2 accept rate: 0% Yes they email the feedback given by the grader along with the scores. (10 Feb '15, 20:06)
 0 cut off looks to be <100 :) answered 11 Feb '15, 11:24 11●1●1 accept rate: 0% How do you know? (11 Feb '15, 11:49) idraumr0★ And how does she know? (11 Feb '15, 12:58) idraumr0★ I imagine she has better contact with the organizers than anyone else. (11 Feb '15, 13:18) superty3★ Is this another troll? Because I am not liking these jokes. (11 Feb '15, 13:34) ketanhwr6★ Lol stop the cut off discussion . We will get to know that anyway in a few days. (11 Feb '15, 14:06) when can we actually expect the results? 2dy or tomorrow? (13 Feb '15, 07:26) Today most probably. They said "We have done a preliminary scan and hope to make an announcement in a day or so." (13 Feb '15, 08:02) ketanhwr6★ They said that yesterday. (13 Feb '15, 08:02) ketanhwr6★ And any word on the cutoff? (13 Feb '15, 10:36) idraumr0★ Nopes. @idraumr mail them asking whether the result will come today or not. I might have irritated them a lot by now :P Also, what did they reply when you asked them about your score? (13 Feb '15, 11:08) ketanhwr6★ if any body has asked them their score and got a reply, pls tell me, i also wanna ask. Also I wont mind asking for cutoff in my mail. Also any news on when the official results would be published? (13 Feb '15, 12:06) @ketanhwr, I essentially got told I've irritated them enough. No word on my score, so I'm not sending anymore mails. (13 Feb '15, 12:29) idraumr0★ It is taking forever and scrambling my brain ;_; (13 Feb '15, 12:50) ketanhwr6★ @idraumr , who told, u irritated them? also when r they planning to give the results? by today? (13 Feb '15, 14:33) showing 5 of 14 show all
 0 Did u send a mail?? answered 13 Feb '15, 17:52 1●1 accept rate: 0%
 0 btw @idraumr, when did u get that mail? so most probably results by 2dy? answered 13 Feb '15, 19:36 11●1●1 accept rate: 0% 1606 hrs is when I got it. (13 Feb '15, 19:47) idraumr0★ if we ask, will he tell our score by mail? (13 Feb '15, 20:32) Don't think so. He already denied idraumr and I think someone else as well. (13 Feb '15, 20:34) superty3★
 0 Did anyone else get a couple of random TLEs in Special Sums because of slow I/O? I rather stupidly forgot to set stdio sync to false :/. By any chance, are they considering that for reevaluation? answered 14 Feb '15, 14:57 1★hackpert 1 accept rate: 0% They are. Slow I/O shouldn't lead to any less marks, as long as your algorithm is correct. (14 Feb '15, 14:58) idraumr0★ They checked my algorithm for P2 .They found it "OK" so they increased my score to 110. I had the same problem. :) (14 Feb '15, 15:01) @idraumr , @animesh_f Thanks! I currently have a 10 :( because I messed up problem 2 completely by mixing up two variable names. Wrote them an email, hoping for a 100 at the very least. (14 Feb '15, 15:03) hackpert1★ Please tell us if they give you any marks for your second problem. (14 Feb '15, 15:06) superty3★ Sure. But I doubt they would, since my code for the second problem is pretty much unreadable with the pre-computations and stuff. (14 Feb '15, 15:12) hackpert1★ Well, just in case they do. (14 Feb '15, 15:13) superty3★ I didn't use any fast I/O but still got 100 in special sums. (14 Feb '15, 18:16) ketanhwr6★ Yeah, once I fixed my mistake I got 100. cout/cin. No fast IO. (14 Feb '15, 18:24) superty3★ showing 5 of 8 show all
 0 In periodic string, in JAVA, it is showing TLE(execution timed out(wall clock time limit exceeded)) and the execution time is 5.6s and 5.8s for the first two input data of subtask 4.But when I ran it on my computer each of those two data sets are taking approximately 1s. Will I be given marks for subtask 4? PS: I used System.currentTimeMillis() for timing.I think there is something wrong with Special Sum also so I am waiting for test data to be downloaded(currently showing 5 hours left) before I finally write for reevaluation. answered 14 Feb '15, 17:37 71●1●2●5 accept rate: 0% By the looks of the previous answer, this is a common issue. Do tell us if you get more marks on reevaluation. (14 Feb '15, 18:09) idraumr0★ @idraumr For periodic string, my solution was "deemed to be" 100/100. I am currently waiting for my response of special sum. (14 Feb '15, 18:54) I had the exact same issue with the same problem (I also code in JAVA) and I wrote to them. They checked my algorithm and they made it 100 after seeing it. Slow I/O error is unfair for JAVA :P (14 Feb '15, 19:11)
 0 I had the same 'wall clock time limit exceeded' error as animesh_f (I used Java too). I've written to them for re-evaluation. I'm yet to get my result. :-( answered 16 Feb '15, 14:51 3★data2000 1●2 accept rate: 0%
 0 I'm interested to know how you guys approached the SPECIALSUMS problem... Can anybody share how you did it? (which algorithm?, what logic?, etc.) answered 16 Feb '15, 16:13 3★data2000 1●2 accept rate: 0% http://inoi15.discuss.codechef.com/questions/63521/problem-1-inoi-2015 (16 Feb '15, 16:19) superty3★
 0 Results are out! http://www.iarcs.org.in/inoi/2015/inoi2015/results_inoi2015.php All the best to all those who qualified. May we have a strong competition at IOITC to get into IOI :) answered 18 Feb '15, 07:39 11●1●1 accept rate: 0% Congrats man! See you at the camp :) (18 Feb '15, 08:07) ketanhwr6★ Congrats everyone! :) (18 Feb '15, 10:36) superty3★ Btw, will anyone appear for JEE? Can they keep the camp after JEE? If anyone is appearing for it, please mail them. Considering the fact that IOI is pretty late this year, so it won't be a problem. (18 Feb '15, 10:53) ketanhwr6★ @ketanhwr, I suppose that will not be possible, as the team has to finish all formalities for travel atleast a month ahead. So, they will try to host the camp (and subsequently select the team) as soon as possible (ie. the starting of May). And the camp has been before JEE (or JEE Advanced) for the past two years. You can ask them to have the camp later, but there is very little chance for that. (18 Feb '15, 13:44) I did an email and the response was that it is impossible to conduct the camp before JEE.Will the class 12th guys still attend the camp ? I'm also a class 12th student and not quite sure about attending it. (19 Feb '15, 21:06)
 0 What was the cutoff? answered 18 Feb '15, 10:18 469●6●30 accept rate: 7% 100 I think. (18 Feb '15, 10:52) ketanhwr6★
 0 What happens at the camp? This was the first year I applied for INOI and didn't qualify for IOITC. Am curious to know.. answered 20 Feb '15, 13:29 1●1●2 accept rate: 0% They teach us with important algos. And then there are tests for 3 days where they select the Indian team for IOI. (20 Feb '15, 14:05) ketanhwr6★
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question asked: 31 Jan '15, 12:42

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last updated: 20 Feb '15, 14:05