2020 ECNU Campus Online Invitational Contest

9 problems from 2020 ECNU Campus Online Invitational Contest (contest 102606), difficulty -. 7/9 solutions verified against sample I/O.

9 items

2020 ECNU Campus Online Invitational Contest

Special | 9 problems | 7/9 verified | Difficulty - | 21m 30s

#	Problem	Time	✓
A	Amateur Chess Players	3m 54s	✓
B	Binary String	2m 35s	✓
C	Coronavirus Battle	1m 37s
D	Decay of Signals	6m 40s
E	Even Degree	1m 32s	✓
F	Find / -type f -or -type d	1m 6s	✓
G	Geralt of Rivia	1m 43s	✓
H	Heat Pipes	1m 10s	✓
I	Idiotic Suffix Array	1m 13s	✓

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606D - Decay of Signals

I can write the full editorial and implementation, but the requested format is much larger than a single response can reliably contain while keeping the explanation, proof, Python solution, tests, and edge-case walkthroughs complete. I can split it into parts: 1.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606B - Binary String

This problem is about discovering a hidden binary string. We are told only its length. The only information available comes from queries: we submit another binary string, and the judge tells us whether our submitted string appears inside the hidden string as a subsequence.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606I - Idiotic Suffix Array

A direct approach would try to build a candidate string, generate all of its suffixes, sort them, and check whether the original suffix has the required rank. This is correct because it exactly follows the definition of the suffix array.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606H - Heat Pipes

We have a graph where each vertex is a greenhouse and each edge is a heat pipe. Every vertex must receive an integer temperature in the range [a, b]. For every edge, the two endpoint temperatures must differ by exactly one.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606G - Geralt of Rivia

Geralt fights a monster that always receives the first hit. Geralt can improve two statistics before the fight: attack and defense. Increasing attack by one point costs a crowns, while increasing defense by one point costs b crowns.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606F - Find / -type f -or -type d

The input describes a filesystem snapshot. Each line is an absolute path that represents either a file or a directory, but the lines are mixed in a random order.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606E - Even Degree

We have an undirected graph where every vertex starts with an even number of incident edges. We may remove edges one by one, but an edge can only be removed if at least one of its two endpoints currently has an even degree.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606C - Coronavirus Battle

I can write the editorial, but the full version requested is much longer than can fit in a single response. I’ll provide it in parts so that each section remains complete and readable. I’ll start with the problem understanding, approaches, and algorithm.

Practice › Codeforces Solutions › 2020 ECNU Campus Online Invitational Contest ›

CF 102606A - Amateur Chess Players

Edit The board contains a small collection of occupied squares. White owns one set of squares and black owns another. A turn consists of deleting one or more of your own remaining squares.