Labib666's blog

JOI Open Contest 2016
By Labib666, history, 9 years ago, In English

Looks like the Japanese Olympiad in Informatics (JOI) Open Contest is going to take place in less than 24 hours. The first round will be held on June 19, 2016: 04:00-09:00 (UTC/GMT).

You can access the contest from this page: http://cms.ioi-jp.org/open-2016/index.html

According to this link:

"This is an IOI-like open competition for students at schools for secondary education. The main purpose of this contest is to give an opportunity to Japanese delegations and candidates of delegations for training and practice. But the contest itself is open to everybody. Everybody is welcome to attend JOI Open Contest 2016!

The duration of the contest is 5 hours. The same contests are held twice (Round 1 and Round 2). Contestants can participate in one of Round 1 or Round 2 according to their time zone. After Round 2 finishes, we will open the judging server for one day. Interested contestants can improve and resubmit their solutions by themselves.re held twice (Round 1 and Round 2).

Registration will be open before each contest. A link to the registration page will appear on this page about 30 minutes before the beginning of each contest. Contestants can register on the contest site by themselves from the right before the beginning of each contest until the end of it.

No prizes will be given to the contestants."

Contest duration
5 hours

The number of tasks
3 tasks

Language
English, Japanese

Round 1
Sunday, June 19, 2016
13:00-18:00 +0900 (JST)
04:00-09:00 (UTC/GMT)

Round 2 (tasks for Round 1 and Round 2 are the same)
Sunday, June 19, 2016
19:00-24:00 +0900 (JST)
10:00-15:00 (UTC/GMT)

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9 years ago, # |
  Vote: I like it +11 Vote: I do not like it

Past JOI Problems: 2015, 2014 and older

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9 years ago, # |
  Vote: I like it +10 Vote: I do not like it

5 hours for 3 problems? :o It seems the problems are gonna too much difficult :(

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    9 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Yeah, IOI style contest are like that. Usually they divide in two days, so 3 problems in 5 hours each day.

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9 years ago, # |
  Vote: I like it +20 Vote: I do not like it

How to solve problem B?

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    9 years ago, # ^ |
    ← Rev. 2   Vote: I like it +16 Vote: I do not like it

    Firstly, sort the N words in lexicographical order.

    Construct two tries. One trie for the original N words and another trie for the original N words, reversed. For the first trie, note that each node corresponds to a subsegment [l, r] of words, since the words are sorted, so we store two indices l, r for each node, representing which words belong to the node of the trie (we can insert the words one by one in sorted order easily). For the second trie, store a vector of indices of words that correspond to the node for each node. (this time it might not be contiguous since we reversed the words)

    Now, for each query, go down the first trie to find the subsegment [l, r] of words with the given prefix. Then, go down the second trie to find the indices of words with the given suffix. Finally, binary search the vector of indices of words with the given suffix and we're done.

    UPD : Apparently the official seems much more complicated than this O_O

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9 years ago, # |
  Vote: I like it +3 Vote: I do not like it

How to solve A and C? They published the source code but it seems alien to me

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    9 years ago, # ^ |
    ← Rev. 2   Vote: I like it +6 Vote: I do not like it

    Agreed. I wrote a blog post asking for help. So far there's no reply yet.

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8 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I participated in this contest and the problems seemed nice. Is there any online judge containing JOI problems?

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