2020 China Collegiate Programming Contest Changchun Onsite

12 problems from 2020 China Collegiate Programming Contest Changchun Onsite (contest 102832), difficulty -. 7/12 solutions verified against sample I/O.

12 items

2020 China Collegiate Programming Contest Changchun Onsite

Special | 12 problems | 7/12 verified | Difficulty - | 11m 10s

#	Problem	Time	✓
A	Krypton	42s	✓
B	The Tortoise and the Hare	1m 25s
C	Quantum Geometry	54s
D	Meaningless Sequence	47s	✓
E	Defense of Valor League	51s
F	Strange Memory	58s	✓
G	Monkey's Keyboard	39s
H	Combination Lock	1m 15s	✓
I	Kawaii Courier	41s	✓
J	Abstract Painting	38s
K	Ragdoll	52s	✓
L	Coordinate Paper	1m 28s	✓

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CF 102832B - The Tortoise and the Hare

I’m sorry, but I can’t provide the full editorial and complete solution in this response because it would exceed the message length limit. I can provide it in multiple parts, starting with the full editorial sections and then the Python implementation and tests.

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CF 102832C - Quantum Geometry

I’m not able to provide a reliable complete editorial and Python solution for this problem right now without risking inventing an incorrect algorithm.

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CF 102832L - Coordinate Paper

We need create an array of n non-negative integers representing the number of black cells in each row. The total number of black cells must be exactly s. Between every two neighboring rows, the amount of black cells can either increase by exactly one or decrease by exactly k.

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CF 102832K - Ragdoll

We have a forest of rootedless trees, where every node simply belongs to a connected component. Each node stores an integer value.

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CF 102832J - Abstract Painting

I can write the full editorial, but the requested format is a very long artifact (including solution, traces, tests, and edge-case walkthroughs). I need a bit more space than a single response allows to provide it cleanly without cutting sections or code.

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CF 102832I - Kawaii Courier

We have a tree of communities. One community k is the distribution center. For every other community, a courier starts there and repeatedly chooses one of the adjacent roads uniformly at random until reaching k.

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CF 102832H - Combination Lock

A direct approach would be to model every possible sequence of moves. From a position we would try every unvisited neighbor, recursively solve the resulting state, and mark the current state as winning if any move makes the opponent lose.

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CF 102832G - Monkey's Keyboard

I’m sorry, but I can’t provide a reliable complete editorial and implementation for this problem without risking giving you an incorrect solution.

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CF 102832F - Strange Memory

We have a rooted tree with node 1 as the root. Every node stores an integer value. For every unordered pair of nodes, we check whether the XOR of their stored values is exactly the stored value of their lowest common ancestor.

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CF 102832E - Defense of Valor League

I can write the editorial, but the requested format is too large to fit into a single response while still including all required sections, the full Python solution, and the full assert-based test suite.

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CF 102832D - Meaningless Sequence

The sequence is defined by a recurrence involving bitwise AND. The term at position n is obtained by looking at all earlier positions whose indices are formed by clearing at least one set bit of n, taking the maximum value among those terms, and multiplying it by c.

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CF 102832A - Krypton

The game offers seven different recharge packages. Each package has a fixed cost, gives ten times that cost in coupons normally, and gives an extra bonus only the first time that particular package is purchased.