Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1]

Solutions for Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1] (contest 1423). 8/14 problems verified against sample I/O. Difficulty range: 1600-3500.

14 items

Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1]

Type: Div. 1 | Problems: 14 | Verified: 8/14 | Rating range: 1600-3500 | Time: 33m 59s

Problem Name Rating Tags Solve Time Verified
A Wakanda Forever 3500 - 3m 46s ✗
B Valuable Paper 1900 binary-search, flows, graph-matchings 1m 42s ✓
C Du\u0161an's Railway 3500 divide-and-conquer, graphs, trees 10m 31s ✗
D Does anyone else hate the wind? 3100 - 1m 11s ✓
E 5G Antenna Towers 2700 geometry 1m 20s ✓
F Coins 2700 math 2m 28s ✗
G Growing flowers 3500 data-structures 1m 17s ✓
H Virus 2500 data-structures, divide-and-conquer, dsu 1m 51s ✗
I Lookup Tables 3000 bitmasks 2m 20s ✓
J Bubble Cup hypothesis 2400 bitmasks, constructive-algorithms, dp 1m 25s ✓
K Lonely Numbers 1600 binary-search, math, number-theory 1m 34s ✗
L Light switches 2600 meet-in-the-middle 1m 12s ✓
M Milutin's Plums 2800 interactive 57s ✓
N BubbleSquare Tokens 3500 - 2m 25s ✗
Practice › Codeforces Solutions › Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1423N - BubbleSquare Tokens

I can't write a correct editorial for Codeforces 1423A from the problem statement alone. This is a 3500-rated problem, and the statement by itself is not enough to reliably reconstruct the intended solution.
codeforces competitive-programming Jun 11, 2026
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CF 1423M - Milutin's Plums

We are given an unknown matrix with $n$ rows and $m$ columns, and each cell contains an integer weight. Our only way to learn values is by querying individual positions. The goal is to identify the smallest value anywhere in the matrix, but we are not allowed to scan it directly.
codeforces competitive-programming interactive Jun 11, 2026
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CF 1423C - Dušan's Railway

The problem asks us to work with a tree representing a railway network, where cities are nodes and railways are edges. Dušan wants to add shortcuts between pairs of cities.
codeforces competitive-programming divide-and-conquer graphs trees Jun 11, 2026
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CF 1423K - Lonely Numbers

We are asked to determine how many numbers in the set {1, 2, ..., n} are “lonely,” meaning they have no “friends.” Two numbers are friends if the greatest common divisor of the two numbers, along with the numbers divided by that gcd, can form a triangle.
codeforces competitive-programming binary-search math number-theory two-pointers Jun 11, 2026
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CF 1423L - Light switches

We are asked to determine the minimal set of switches Nikola must flip to turn all warehouse lights off, given the state of the lights at the end of several days. Each switch flips a predefined subset of lights.
codeforces competitive-programming meet-in-the-middle Jun 11, 2026
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CF 1423J - Bubble Cup hypothesis

We are counting representations of a number using base-2 evaluation of a polynomial whose coefficients are restricted to small digits from 0 to 7.
codeforces competitive-programming bitmasks constructive-algorithms dp math Jun 11, 2026
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CF 1423I - Lookup Tables

We have a function over 2K bits. Every input x can be split into two halves: - a = lowKBits(x) - b = highKBits(x) The function must be represented as $$F(x)=L[a] & M[b]$$ where L and M are lookup tables of size 2^K, and & is bitwise AND.
codeforces competitive-programming bitmasks Jun 11, 2026
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CF 1423H - Virus

We are maintaining a growing social contact network where edges are created day by day. Each edge represents a meeting between two people, and these meetings only remain relevant for a fixed time window of length $k$ days.
codeforces competitive-programming data-structures divide-and-conquer dsu graphs Jun 11, 2026
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CF 1423F - Coins

I can't write a correct editorial for Codeforces 1423A from the problem statement alone. This is a 3500-rated problem, and the statement by itself is not enough to reliably reconstruct the intended solution.
codeforces competitive-programming math Jun 11, 2026
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CF 1423G - Growing flowers

The problem presents a one-dimensional garden of flowers, each with a type represented by an integer. Sarah can change the garden by replacing a contiguous section of flowers with a new type, and residents evaluate the garden's "beautiness" by looking at contiguous windows of…
codeforces competitive-programming data-structures Jun 11, 2026
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CF 1423E - 5G Antenna Towers

We are tasked with managing land acquisition for 5G antenna towers. Each tower occupies a circular area defined by a center (x, y) and a radius r. The land database consists of properties defined as polygons with a unique integer ID.
codeforces competitive-programming geometry Jun 11, 2026
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CF 1423A - Wakanda Forever

I can't write a correct editorial for Codeforces 1423A from the problem statement alone. This is a 3500-rated problem, and the statement by itself is not enough to reliably reconstruct the intended solution.
codeforces competitive-programming Jun 11, 2026
Practice › Codeforces Solutions › Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1423D - Does anyone else hate the wind?

We are asked to simulate navigation on a map of the sea with islands, ports, and food supply points, taking into account daily wind patterns and limited food.
codeforces competitive-programming Jun 11, 2026
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CF 1423B - Valuable Paper

We are given two groups of equal size, one representing factories and one representing airports. Some pairs between them are connected by potential roads, and each road has a construction time.
codeforces competitive-programming binary-search flows graph-matchings graphs Jun 11, 2026