Good Bye 2023

Solutions for Good Bye 2023 (contest 1916). 5/9 problems verified against sample I/O. Difficulty range: 800-3500.

9 items

Good Bye 2023

Type: Special | Problems: 9 | Verified: 5/9 | Rating range: 800-3500 | Time: 14m 35s

Problem	Name	Rating	Tags	Solve Time	Verified
A	2023	800	constructive-algorithms, implementation, math	2m 35s	✓
B	Two Divisors	1000	constructive-algorithms, math, number-theory	38s	✗
C	Training Before the Olympiad	1200	constructive-algorithms, games, greedy	1m 52s	✗
D	Mathematical Problem	1700	brute-force, constructive-algorithms, geometry	38s	✗
E	Happy Life in University	2300	data-structures, dfs-and-similar, greedy	2m 11s	✓
F	Group Division	2900	constructive-algorithms, dfs-and-similar, graphs	2m 6s	✗
G	Optimizations From Chelsu	3500	divide-and-conquer, dp, number-theory	2m 3s	✓
H1	Matrix Rank (Easy Version)	2700	brute-force, combinatorics, dp	1m 25s	✓
H2	Matrix Rank (Hard Version)	2700	combinatorics, dp, math	1m 7s	✓

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916H2 - Matrix Rank (Hard Version)

We are asked to count the number of $n times n$ matrices over a finite field of size $p$ (integers modulo a prime $p$) that have an exact rank $r$, for every $r$ from 0 to $k$.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916H1 - Matrix Rank (Easy Version)

We are working over an $n times n$ matrix whose entries lie in a finite field of size $p$, meaning every entry is an integer modulo $p$ and arithmetic behaves like linear algebra over a field.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916G - Optimizations From Chelsu

We are given a tree whose edges carry positive integer weights. For any two vertices $u$ and $v$, let $len(u,v)$ be the number of edges on their path, and let $gcd(u,v)$ be the gcd of all edge weights on that path.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916F - Group Division

We are given a social graph of students at a school, with some known friendly connections. The total number of students is $n1 + n2$, where $n1$ and $n2$ are the desired sizes of two distinct groups: computer scientists and mathematicians.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916E - Happy Life in University

We are given a rooted tree. Each node has a label representing an “activity type”. For any two nodes $u$ and $v$, we look at their lowest common ancestor $w$.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916A - 2023

We start with an unknown array a whose product of all elements is exactly 2023. Some k elements were removed, leaving the array b of length n. The task is to determine whether such an original array could exist. If it can, we must output any valid set of k removed numbers.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916C - Training Before the Olympiad

We are given an array and asked to repeatedly reduce it until only one number remains. A move picks two elements, removes them, and inserts a new value derived from their sum: take the average of the pair, round it down, and then multiply by two.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916D - Mathematical Problem

We are asked to construct a set of numbers with a very specific structure. Each test case provides an odd integer $n$, which has a dual meaning: it is both the number of numbers we need to produce and the number of digits each of those numbers must have.

Practice › Codeforces Solutions › Good Bye 2023 ›

CF 1916B - Two Divisors

We are given two integers, $a$ and $b$, which are the two largest proper divisors of some unknown integer $x$. Here, $1 le a < b < x$, and our task is to find any integer $x$ that fits this description.