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rebornplusplus's blog

Views on Subtasks in a Round
By rebornplusplus, history, 5 years ago, In English

What do you think about having sub-tasks in a round?

I noticed, recently, that there has been some rounds consisting of a few problems differing with one another only by constraints. I am curious what does the community think about it. Is it good, bad or something more?

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5 years ago, # |
  Vote: I like it +31 Vote: I do not like it

Usually, we introduce subtasks if we want to avoid a probable gap between problems. For example, here C1 made the round more interesting for ~3000 participants. Strong issues would not have appeared if it was absent, but don't forget about thousands of participants for whom D+ were too difficult. Similarly, the gap between F and G2 is looked to be huge, and I've introduced G1.

In a perfect world, probably, subtasks are not needed. But in the real world, sometimes, it is not easy to estimate problem difficulties. Also, problems are not snacks — you can't easily get new or replace them with some extra. I see that a subtask is a method to make difficulties smoother, to make round interesting for more participants. Without subtasks imbalanced rounds will appear more often.

This time I overestimated G1, it should cost less. But I think that easy versions should cost reasonable scores. Say, here 2000+1500 would be much better. For example, I see that C1 and C2 cost reasonable.

As I wrote in the comment we need to improve the support of subtasks to reduce motivation to solve easy versions separately.

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    5 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it

    I suggest flipping the scoring scheme for subtasks, give more points to the harder one so people solve the harder one first to gain more points as it will be more fruitful that way

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    5 years ago, # ^ |
      Vote: I like it +78 Vote: I do not like it

    Personally I feel subtask questions are more suited when penalty is last successful submission time.

    Also I feel since codeforces have allowed its own version rounds and ICPC type rounds. Maybe one or two experimental contests or last successful submission time would also sound good and then you can give maybe similar to ioi, 4 to 5 question with 2 or 3 subtasks each and 2 hours time for such a contest. I would prefer Div3 contests to have such flavour because it will encourage more beginners to aim at subtasks and not idle away time.

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