Блог пользователя erniepsycholone

Автор erniepsycholone, 9 месяцев назад, По-английски

1933A - Turtle Puzzle: Rearrange and Negate

Idea: snowysecret, prepared: snowysecret

Tutorial
Solution

1933B - Turtle Math: Fast Three Task

Idea: snowysecret, prepared: snowysecret, erniepsycholone

Tutorial
Solution

1933C - Turtle Fingers: Count the Values of k

Idea: dbsbs, prepared: dbsbs, snowysecret

Tutorial
Solution

1933D - Turtle Tenacity: Continual Mods

Idea: snowysecret, erniepsycholone, prepared: snowysecret

Tutorial
Solution

1933E - Turtle vs. Rabbit Race: Optimal Trainings

Idea: snowysecret, prepared: snowysecret

Tutorial
Solution

1933F - Turtle Mission: Robot and the Earthquake

Idea: erniepsycholone, prepared: erniepsycholone

Hint
Tutorial
Solution

1933G - Turtle Magic: Royal Turtle Shell Pattern

Idea: snowysecret, jerryliuhkg, prepared: snowysecret

Tutorial
Solution

Hope the contest was in some way helpful in improving your skills, and that you all had fun!

“If you only do what you can do, you will never be more than you are now.” – Master Oogway

Разбор задач Codeforces Round 929 (Div. 3)
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9 месяцев назад, # |
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This Round was really amazing. I really enjoyed this round. The problems are very good.

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9 месяцев назад, # |
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For the problem F tutorial (spoiler alert): I don't understand this part: "Finally, choose the best among all n tiles after waiting for the endpoint to cycle back." can someone explain it to me?

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    9 месяцев назад, # ^ |
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    Let $$$b_i$$$ be the minimum time needed to reach cell $$$(i, m-2)$$$ in the transformed problem. Then, it takes $$$b_i + 1$$$ time to reach cell $$$(i, m-1)$$$ in the transformed problem.

    The transformation we did is to imagine the robot moving down instead of the rocks moving up. Therefore in reality it takes $$$b_i + 1$$$ time to reach cell $$$(c_i, m-1)$$$ where $$$c_i = (i-(b_i+1)) \bmod n$$$. Hence, to reach $$$(n-1, m-1)$$$ we really need $$$b_i + 1 + \min(c_i + 1, n - 1 - c_i)$$$ time.

    Therefore the answer is just $$$\min_{i=0}^{n-1} b_i + 1 + \min(c_i + 1, n - 1 - c_i)$$$ where $$$b$$$ and $$$c$$$ arrays are defined above.

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      9 месяцев назад, # ^ |
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      thanks a lot buddy

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      9 месяцев назад, # ^ |
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      I have seen solution for same problem via simple bfs to reach to end position how come that solution works scratching my head on that for a while

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9 месяцев назад, # |
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Can anyone explain why unordered_set TLEs for question D but set doesn't?

unordered_set: https://mirror.codeforces.com/contest/1933/submission/248601138

set: https://mirror.codeforces.com/contest/1933/submission/249214209

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    9 месяцев назад, # ^ |
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    Because there time complexity goes in order of O(n) in worst case and the same happens with unordered map also, while in simple amp and set the time complexity remains O(logn).

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9 месяцев назад, # |
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For F,I dont understand why the row update 3 times like"for(int j=0;j<3*n;j++)".I try using 2 times and get WA,3 times AC.HOW?

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    9 месяцев назад, # ^ |
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    As RT can go from $$$(x,y)$$$ to $$$((x+2) \text{ mod } n,y)$$$, if x=0 currently, and $$$n \text{ mod } 2=1$$$, it would require the 2 times you mentioned. However, if $$$x!=0$$$, we need to loop $$$3$$$ times to run an entire cycle throughout a column. An example would be if RT is at $$$(3,0)$$$, with $$$n=5$$$, the following operations would be needed to run through column $$$0$$$:

    $$$(3,0)$$$ --> $$$(0,0)$$$ --> $$$(2,0)$$$ --> $$$(4,0)$$$ --> $$$(1,0)$$$ --> $$$(3,0)$$$

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      9 месяцев назад, # ^ |
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      Thanks a lot!!

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      9 месяцев назад, # ^ |
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      Hello,I still don't understand.I used"for(int i=0;i<200*n;i++)for(int j=0;j<m;j++)" and WA on test 36. Why we should run m before n?my submission

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      5 месяцев назад, # ^ |
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      Hi, but why should it complete a cycle? like in 2 loops it is able to reach till (1,0), why should it get back to (3,0)? (my assumption is that the optimal path to reach is starting at (3,0) so going a loop back to (3,0) seems redundant)

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9 месяцев назад, # |
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Thank you for the great round!) I've finally got the pupil)

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9 месяцев назад, # |
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I tried to solve problem E using ternary search but it gave TLE on 8th test case (https://mirror.codeforces.com/contest/1933/submission/249501917), can anyone share the ternary search solution for problem E.

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9 месяцев назад, # |
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In E, they used the following formula to calculate the first t terms of an arithmetic series: ~~~~~ int ut = (u + (u — t + 1)) * t / 2; ~~~~~ But it is wrong because u-t+1 might be negative, and in that case, the standard formula doesn't work, but why does it pass the test cases?

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9 месяцев назад, # |
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my solution for problem E : https://mirror.codeforces.com/contest/1933/submission/249920547

i feel my way of applying binary search here is much easier , compared to the other solutions i saw

feel free to let me know what u think !!

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9 месяцев назад, # |
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https://ibb.co/nR5Cb0Z

I don’t really get this part. I mean why do we need this part for implementing and how to come up with the formula i + floor(j/2), j + floor(i/2),… Please help me with this. Thank you!

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8 месяцев назад, # |
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Round was overall really good. Thanks.

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8 месяцев назад, # |
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I am encountering an issue with Problem E: Turtle vs. Rabbit Race — Optimal Trainings. My solution, which produces the expected output locally on my IDE, is being marked as incorrect on Codeforces, specifically in the first test case. Here, is my submission link 253865555