Hello 2019

8 problems from Hello 2019 (contest 1097), difficulty 800-3400. 5/8 solutions verified against sample I/O.

8 items

Hello 2019

Special | 8 problems | 5/8 verified | Difficulty 800-3400 | 33m 15s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Gennady and a Card Game	800	brute-force, implementation	43,794	1m 17s	✓
B	Petr and a Combination Lock	1200	bitmasks, brute-force, dp	35,929	3m 57s	✓
C	Yuhao and a Parenthesis	1400	greedy, implementation	8,783	4m 37s	✓
D	Makoto and a Blackboard	2200	dp, math, number-theory	3,169	3m 58s	✓
E	Egor and an RPG game	3400	constructive-algorithms, greedy	534	4m 4s
F	Alex and a TV Show	2500	bitmasks, combinatorics, number-theory	1,472	1m 21s	✓
G	Vladislav and a Great Legend	3000	combinatorics, dp, trees	1,054	6m 10s
H	Mateusz and an Infinite Sequence	3400	bitmasks, brute-force, dp	139	7m 51s

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097H - Mateusz and an Infinite Sequence

We are working with an infinite sequence that is not written explicitly, but generated recursively. The construction starts from a single value zero.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097G - Vladislav and a Great Legend

We are working with a tree where every subset of vertices defines a natural “cost” based on how large a minimal connected subgraph is when we are forced to include all vertices in that subset.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097C - Yuhao and a Parenthesis

We are given a collection of bracket strings, each string being some mixture of opening and closing parentheses. From these strings, we are allowed to form disjoint pairs.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097E - Egor and an RPG game

We are given a permutation and we must break it into several subsequences taken in order from the original array. Each element must belong to exactly one subsequence. Every subsequence must be strictly monotone, either strictly increasing or strictly decreasing.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097D - Makoto and a Blackboard

We start with a single integer placed on a board. At each step, this number is replaced by one of its divisors, chosen uniformly at random.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097B - Petr and a Combination Lock

We are given a circular lock that behaves like a 360-degree dial. Starting from zero, we perform a sequence of rotations, each rotation having a fixed magnitude, but we are free to choose its direction: clockwise or counterclockwise.

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097F - Alex and a TV Show

We are asked to simulate operations on a set of multisets, each initially empty. The operations are either assigning a single value to a multiset, combining two multisets via union, combining two multisets via a multiset product using greatest common divisors, or querying the…

Practice › Codeforces Solutions › Hello 2019 ›

CF 1097A - Gennady and a Card Game

The game Gennady plays involves matching cards either by rank or suit. In practical terms, you are given a single card on the table and a hand of five cards.