Codeforces Global Round 1

Solutions for Codeforces Global Round 1 (contest 1110). 5/8 problems verified against sample I/O. Difficulty range: 900-3500.

8 items

Codeforces Global Round 1

Type: Global | Problems: 8 | Verified: 5/8 | Rating range: 900-3500 | Time: 15m 41s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Parity	900	math	5m 9s	✗
B	Tape	1400	greedy, sortings	1m 32s	✓
C	Meaningless Operations	1500	constructive-algorithms, math, number-theory	1m 33s	✓
D	Jongmah	2200	dp	1m 38s	✗
E	Magic Stones	2200	constructive-algorithms, math, sortings	1m 10s	✓
F	Nearest Leaf	2600	data-structures, trees	1m 17s	✓
G	Tree-Tac-Toe	3100	constructive-algorithms, games, trees	1m 4s	✓
H	Modest Substrings	3500	dp, strings	2m 18s	✗

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CF 1110H - Modest Substrings

We are asked to construct a digit string of fixed length n. Every substring of this string is interpreted as a number (ignoring leading zeros), and we get a score of 1 for a substring if that number lies in the inclusive interval [l, r].

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CF 1110A - Parity

The problem gives a number $n$ not in decimal form, but in some arbitrary base $b$. The digits of $n$ are listed from the most significant to the least significant, and the task is to decide whether $n$ is even or odd in decimal.

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CF 1110G - Tree-Tac-Toe

We are asked to analyze a game of tic-tac-toe played on a tree. Each vertex is either uncolored or already white. Two players alternate coloring vertices, starting with white. The first player to complete a path of three vertices in their color wins.

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CF 1110F - Nearest Leaf

We are given a rooted tree where the parent of each node is fixed by input order: node i connects to some earlier node pi, forming a rooted structure at node 1.

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CF 1110D - Jongmah

We are given a multiset of tiles, where each tile carries an integer value between 1 and m. The goal is to repeatedly pick disjoint groups of exactly three tiles and form as many such groups as possible.

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CF 1110E - Magic Stones

We are given an array of integers representing charges on a line of stones. A single operation picks any interior position and replaces its value using its two neighbors: the new value becomes the sum of the left and right neighbors minus its old value.

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CF 1110B - Tape

We are given a sorted list of positions on a long line segment where damage has occurred. Each damaged position must be covered by tape, but the tape does not need to avoid healthy positions, it can freely cover anything in between.

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CF 1110C - Meaningless Operations

We are given a number $a$. For this number we are allowed to pick any $b$ such that $1 le b < a$. For each choice of $b$, we compute two values derived from bitwise operations: one is $a oplus b$, the other is $a & b$. We then take the gcd of these two results.