Unknown Language Round 2

9 problems from Unknown Language Round 2 (contest 72), difficulty 1000-2300. 8/9 solutions verified against sample I/O.

9 items

Unknown Language Round 2

Special | 9 problems | 8/9 verified | Difficulty 1000-2300 | 21m 37s

# Problem Rating Tags Accepted Time ✓
A Goshtasp, Vishtasp and Eidi 1800 *special, greedy, math 194 1m 18s ✓
B INI-file 2200 *special, implementation 117 1m 45s ✓
C Extraordinarily Nice Numbers 1200 *special, math 1,052 1m 26s ✓
D Perse-script 2300 *special, expression-parsing 83 1m 55s
E Ali goes shopping 1800 *special, brute-force, strings 181 7m 34s ✓
F Oil 1900 *special, greedy, math 143 1m 43s ✓
G Fibonacci army 1000 *special, dp 2,833 1m 16s ✓
H Reverse It! 1600 *special, implementation 284 3m 28s ✓
I Goofy Numbers 1500 *special, implementation 483 1m 12s ✓
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72A - Goshtasp, Vishtasp and Eidi

The problem asks us to decide whether a positive integer $n$ can be represented as a sum of distinct integers, where each integer is either 1 or a prime number. If such a representation exists, we need to produce one that is lexicographically largest.
codeforces competitive-programming *special greedy math May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72B - INI-file

We are given a text file written in INI format. Every meaningful line is either a section declaration such as [network] or a key-value assignment such as port=8080. Spaces around keys, values, and section brackets are irrelevant and must be removed in the final output.
codeforces competitive-programming *special implementation May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72C - Extraordinarily Nice Numbers

We are asked to determine whether a positive integer $x$ is extraordinarily nice. By the problem's definition, a number is extraordinarily nice if it has exactly the same number of even divisors as odd divisors. The input is a single integer $x$ between 1 and 1000.
codeforces competitive-programming *special math May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72D - Perse-script

We are asked to evaluate a string expression in a small function-based language. Every string literal is enclosed in quotes, and there are only four types of functions: concat, reverse, and substr in two forms. Each function operates only on strings or integers as indices.
codeforces competitive-programming *special expression-parsing May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72E - Ali goes shopping

We are given a lowercase string and must find the substring that appears the largest number of times inside it. Occurrences may overlap. Among all substrings with the same maximum frequency, we choose the longest one.
codeforces competitive-programming *special brute-force strings May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72F - Oil

We have an n × m grid. Some entire rows are empty, some entire columns are empty, and every empty cell belongs to at least one of those empty rows or empty columns. All remaining cells contain oil.
codeforces competitive-programming *special greedy math May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72G - Fibonacci army

The problem asks us to compute the n-th Fibonacci number, but with a slight twist in indexing: the sequence starts with f₀ = 1, f₁ = 1. Every subsequent number is the sum of the previous two.
codeforces competitive-programming *special dp May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72H - Reverse It!

The task is to reverse a number given as a string, taking care of signs and leading zeros. The input can be a very large integer, up to 10,000 digits, possibly with leading zeros.
codeforces competitive-programming *special implementation May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72I - Goofy Numbers

We are asked to classify a single non-negative integer based on how it relates to its digits. Specifically, each digit of the number is considered as a potential divisor.
codeforces competitive-programming *special implementation May 28, 2026