Good Bye 2022: 2023 is NEAR

Solutions for Good Bye 2022: 2023 is NEAR (contest 1770). 3/8 problems verified against sample I/O. Difficulty range: 1000-3500.

8 items

Good Bye 2022: 2023 is NEAR

Type: Special | Problems: 8 | Verified: 3/8 | Rating range: 1000-3500 | Time: 16m 49s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Koxia and Whiteboards	1000	brute-force, greedy	3m	✓
B	Koxia and Permutation	1000	constructive-algorithms	2m 29s	✗
C	Koxia and Number Theory	1700	brute-force, chinese-remainder-theorem, math	1m 21s	✓
D	Koxia and Game	2000	constructive-algorithms, data-structures, dfs-and-similar	1m 51s	✗
E	Koxia and Tree	2400	combinatorics, dfs-and-similar, dp	2m 4s	✗
F	Koxia and Sequence	3100	bitmasks, combinatorics, dp	2m 5s	✗
G	Koxia and Bracket	3400	divide-and-conquer, fft, math	1m 32s	✓
H	Koxia, Mahiru and Winter Festival	3500	constructive-algorithms	2m 27s	✗

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770H - Koxia, Mahiru and Winter Festival

This is a Type B (prove inequality) problem, not Type C. The task is to prove that $$frac1{a^3(b+c)}+frac1{b^3(c+a)}+frac1{c^3(a+b)}ge frac32$$ for all positive $a,b,c$ satisfying $abc=1$.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770F - Koxia and Sequence

We are asked to work with sequences of non-negative integers of length $n$. Each sequence must satisfy two conditions: the sum of its elements equals $x$, and the bitwise OR of all its elements equals $y$.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770G - Koxia and Bracket

We are given a string composed entirely of opening and closing parentheses, and we are asked to make it balanced by removing the fewest possible characters.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770E - Koxia and Tree

We are given a tree with $n$ vertices and $k$ butterflies initially located on distinct vertices. Each edge in the tree will be randomly directed, and butterflies can move along edges if the starting vertex has a butterfly and the target vertex is empty.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770D - Koxia and Game

We are given two arrays, a and b, each of length n, with elements between 1 and n. We have to choose a third array c of the same length so that a constructed game is won by Koxia. The game proceeds in n rounds.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770A - Koxia and Whiteboards

We start with an array of numbers placed on whiteboards. Then we are given a sequence of replacement values. Each replacement operation allows us to pick any one whiteboard and overwrite its current value with the new value from the operation.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770B - Koxia and Permutation

This is a Type B (prove inequality) problem, not Type C. The task is to prove that $$frac1{a^3(b+c)}+frac1{b^3(c+a)}+frac1{c^3(a+b)}ge frac32$$ for all positive $a,b,c$ satisfying $abc=1$.

Practice › Codeforces Solutions › Good Bye 2022: 2023 is NEAR ›

CF 1770C - Koxia and Number Theory

We are given an array of positive integers and we are allowed to choose a single positive shift value $x$. After shifting every element by the same amount, we want every pair of resulting numbers to be coprime. Equivalently, we transform the array into $bi = ai + x$.