Unknown Language Round 4

Solutions for Unknown Language Round 4 (contest 130). 10/10 problems verified against sample I/O. Difficulty range: 900-2300.

10 items

Unknown Language Round 4

Type: Special | Problems: 10 | Verified: 10/10 | Rating range: 900-2300 | Time: 16m 22s

Problem Name Rating Tags Solve Time Verified
A Hexagonal numbers 900 *special, implementation 1m 24s ✓
B Gnikool Ssalg 1400 *special, implementation, strings 1m 24s ✓
C Decimal sum 1500 *special 1m 48s ✓
D Exponentiation 1500 *special 1m 51s ✓
E Tribonacci numbers 1600 *special 2m 6s ✓
F Prime factorization 1600 *special 1m 48s ✓
G CAPS LOCK ON 1700 *special 1m 28s ✓
H Balanced brackets 1600 *special 1m 16s ✓
I Array sorting 2300 *special, sortings 1m 47s ✓
J Date calculation 1800 *special 1m 30s ✓
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130A - Hexagonal numbers

We need to compute the $n$-th hexagonal number. The sequence is defined by the formula $$hn = 2n^2 - n$$ The input contains a single integer $n$, and the output is the value produced by this formula.
codeforces competitive-programming *special implementation May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130B - Gnikool Ssalg

The problem asks us to reverse a string. Given a sequence of characters, the output should be the same sequence but in the opposite order, so that the first character becomes the last, the second becomes the second-to-last, and so on.
codeforces competitive-programming *special implementation strings May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130C - Decimal sum

We are given a sequence of integers and need to compute their total sum. The input starts with an integer n, which tells us how many numbers follow. Each of the next n lines contains one element of the array. The task is simply to add all of them together and print the result.
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130D - Exponentiation

We need to compute the remainder when $a^b$ is divided by $c$. The input gives three integers, one per line. The first value is the base, the second is the exponent, and the third is the modulus. The direct interpretation is straightforward.
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130E - Tribonacci numbers

We are asked to compute the n-th Tribonacci number, but only its value modulo 26. The sequence starts with: $$t0 = 0,quad t1 = 0,quad t2 = 1$$ and every later value is formed by summing the previous three: $$ti = t{i-1} + t{i-2} + t{i-3}$$ The input contains a single integer n…
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130F - Prime factorization

The task is to decompose a given integer n into its prime factors and print them in non-decreasing order, with each prime repeated according to its multiplicity. Essentially, if a number is a product of primes like $n = 2^2 cdot 3^1 cdot 5^2$, the output should be 2 2 3 5 5.
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130G - CAPS LOCK ON

We are given a single string containing printable ASCII characters. Some characters may be lowercase English letters, some may already be uppercase letters, and others may be symbols or digits.
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130H - Balanced brackets

We are asked to determine if a string of round brackets is balanced. A balanced sequence is one where every opening bracket «(» has a corresponding closing bracket «)», and brackets are properly nested.
codeforces competitive-programming *special May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130I - Array sorting

We are given an array of at most 100 integers. Every value lies between 1 and 60. The task is simply to print the array in non-decreasing order.
codeforces competitive-programming *special sortings May 28, 2026
Practice › Codeforces Solutions › Unknown Language Round 4 ›

CF 130J - Date calculation

We are given a year in the Gregorian calendar and a day number inside that year. The task is to determine the actual calendar date corresponding to that day number.
codeforces competitive-programming *special May 28, 2026