Codeforces Global Round 13

9 problems from Codeforces Global Round 13 (contest 1491), difficulty 800-3500. 3/9 solutions verified against sample I/O.

9 items

Codeforces Global Round 13

Global | 9 problems | 3/9 verified | Difficulty 800-3500 | 30m

#	Problem	Rating	Tags	Accepted	Time	✓
A	K-th Largest Value	800	brute-force, greedy, implementation	19,018	2m 25s	✓
B	Minimal Cost	1200	brute-force, math	14,230	3m 15s
C	Pekora and Trampoline	1700	brute-force, data-structures, dp	8,394	3m 14s
D	Zookeeper and The Infinite Zoo	1800	bitmasks, constructive-algorithms, dp	8,285	2m 3s	✓
E	Fib-tree	2400	brute-force, dfs-and-similar, divide-and-conquer	2,337	1m 35s	✓
F	Magnets	2700	binary-search, constructive-algorithms, interactive	1,132	3m 38s
G	Switch and Flip	2800	constructive-algorithms, graphs, math	1,008	3m 25s
H	Yuezheng Ling and Dynamic Tree	3400	data-structures, trees	1,209	6m 15s
I	Ruler Of The Zoo	3500	brute-force, data-structures	108	4m 10s

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CF 1491H - Yuezheng Ling and Dynamic Tree

We are given a rooted tree where every node except the root has a parent pointer, so the structure is initially encoded as an array a[i] describing the parent of node i.

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CF 1491I - Ruler Of The Zoo

We are simulating a deterministic elimination process over a queue of animals where each animal has three different strength modes depending on how many consecutive fights it has already won.

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CF 1491G - Switch and Flip

We start with a permutation placed on positions from 1 to n. Each position contains a coin with a label, and every coin also has a direction state, initially all facing up.

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CF 1491F - Magnets

We are given a set of magnets, each secretly belonging to one of three types: North, South, or a special “inactive” type that produces no magnetic behavior.

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We are given a grid that has a very unusual shape: it has n rows and a very large number of columns, from 0 up to 10^6 + 1. Each row contains exactly one obstacle placed at a given column position a[i]. These obstacles block movement through their cells.

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CF 1491C - Pekora and Trampoline

We are given an array of trampoline strengths arranged in a line. Each trampoline behaves like a forced jump: if Pekora lands on position i, she is immediately launched to i + S[i].

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CF 1491E - Fib-tree

We are given a tree with $n$ vertices, and we want to determine whether it is a Fib-tree. A Fib-tree is a tree whose size equals some Fibonacci number $Fk$, and it either consists of a single vertex or can be split into two smaller Fib-trees by removing exactly one edge.

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CF 1491D - Zookeeper and The Infinite Zoo

We are asked to determine reachability in an infinite directed graph. Each vertex is a positive integer, and there is a directed edge from vertex $u$ to vertex $u+v$ if and only if the bitwise AND of $u$ and $v$ equals $v$.

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CF 1491A - K-th Largest Value

We are working with a binary array where every position contains either 0 or 1. The array changes over time through two types of operations. One operation flips a single position from 0 to 1 or from 1 to 0.

Codeforces Global Round 13

Codeforces Global Round 13

CF 1491H - Yuezheng Ling and Dynamic Tree

CF 1491I - Ruler Of The Zoo

CF 1491G - Switch and Flip

CF 1491F - Magnets

CF 1491B - Minimal Cost

CF 1491C - Pekora and Trampoline

CF 1491E - Fib-tree

CF 1491D - Zookeeper and The Infinite Zoo

CF 1491A - K-th Largest Value