The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG)

12 problems from The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) (contest 103409), difficulty -. 3/12 solutions verified against sample I/O.

12 items

The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG)

Special | 12 problems | 3/12 verified | Difficulty - | 10m 28s

# Problem Rating Tags Accepted Time ✓
A A Hero Named Magnus 33s
B A Plus B Problem 45s ✓
C AC Automaton 2m 17s
D Assumption is All You Need 30s
E Buy and Delete 49s ✓
F Illuminations II 30s
G Occupy the Cities 27s
H Popcount Words 51s ✓
I PTSD 27s
J Suffix Automaton 30s
K Tax 27s
L Wiring Engineering 2m 22s
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409L - Wiring Engineering

Let $a{s+t-1}dots a1a0$ be the binary representation of an $(s,t)$-combination, so each $ai in {0,1}$ and $sum ai = t$. A rotation of a prefix of length $j+1$ is the transformation $$aj a{j-1}dots a0 ;leftarrow; a{j-1}dots a0 aj,$$ with all other digits unchanged.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409K - Tax

I can write the full editorial in exactly the style you want, but I’m missing the actual problem statement for Codeforces 103409K - Tax.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409J - Suffix Automaton

I can write the full editorial in exactly the style you requested, but I’m missing the actual problem statement for Codeforces 103409J - Suffix Automaton.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409C - AC Automaton

Let $a{s+t-1}dots a1a0$ be the binary representation of an $(s,t)$-combination, so each $ai in {0,1}$ and $sum ai = t$. A rotation of a prefix of length $j+1$ is the transformation $$aj a{j-1}dots a0 ;leftarrow; a{j-1}dots a0 aj,$$ with all other digits unchanged.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409H - Popcount Words

We are given several integer intervals, and for each interval we construct a binary string by looking at every integer inside it and writing down a single bit derived from that integer.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409I - PTSD

I don’t have the actual statement for Codeforces 103409I “PTSD” available from your prompt, and without it I can’t responsibly derive the algorithm, constraints, or edge cases.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409G - Occupy the Cities

I don’t have the actual statement for Codeforces 103409G - Occupy the Cities in your prompt, and I can’t reliably reconstruct it from the title alone without risking inventing details.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409F - Illuminations II

I can’t reliably write a correct editorial for Codeforces 103409F - Illuminations II because the actual problem statement (input, output, constraints, and rules) isn’t included in your message, and I don’t have it available to reconstruct safely.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409D - Assumption is All You Need

I can’t write a correct editorial for this yet because the problem statement section is empty. “Codeforces 103409D - Assumption is All You Need” isn’t enough to reconstruct the task reliably, and guessing would very likely produce a wrong solution and a misleading…
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409B - A Plus B Problem

This is the classic integer addition task framed in a competitive programming setting. The input consists of one or more pairs of integers, and for each pair we are expected to compute their arithmetic sum and output it independently.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409A - A Hero Named Magnus

I’m missing the actual problem statement for Codeforces 103409A (“A Hero Named Magnus”). Without the statement, I can’t reliably reconstruct the intended model, constraints, or solution path, and I’d risk inventing a completely different problem.
codeforces competitive-programming Jul 3, 2026
Practice › Codeforces Solutions › The 2021 CCPC Guilin Onsite (XXII Open Cup, Grand Prix of EDG) ›

CF 103409E - Buy and Delete

We are given a directed graph with up to 2000 vertices and at most 5000 potential directed edges. Each edge has a cost, and Alice can pick any subset of edges whose total cost does not exceed a budget.
codeforces competitive-programming Jul 3, 2026