brain

tamnd's digital brain — notes, problems, research

41561 notes

CF 102979G - Generate The Array

Let Theorem W be applied to the torus $T(m1,dots,mn)$ with cross order as in Section 7.2.1.3, and let $S$ be an initial segment in that order.

codeforcescompetitive-programming
CF 102979I - Integer Array Shuffle

The prompt is missing the actual problem statement for “Codeforces 102979I - Integer Array Shuffle”, so there is not enough information to reconstruct the task, constraints, or required transformation.

codeforcescompetitive-programming
CF 102979H - Hotspot-2

I can’t reliably write a correct editorial for Codeforces 102979H - Hotspot-2 because the actual problem statement, constraints, and I/O format are missing from your prompt.

codeforcescompetitive-programming
CF 102979F - Find the XOR

We are given a connected undirected graph with up to 100,000 vertices and edges. Each edge has a nonnegative weight.

codeforcescompetitive-programming
CF 102979C - Colorful Squares

Let Theorem W be applied to the torus $T(m1,dots,mn)$ with cross order as in Section 7.2.1.3, and let $S$ be an initial segment in that order.

codeforcescompetitive-programming
CF 102979E - Expected Distance

The problem statement is missing, so I can’t safely derive the model, the solution, or any correctness argument yet.

codeforcescompetitive-programming
CF 102979D - Designing a PCB

We are given a line of pads placed on a straight horizontal axis. Each pad is located at an integer coordinate, and every pad is labeled with a number from 1 to n, with each label appearing exactly twice.

codeforcescompetitive-programming
CF 102979B - Best Meeting Places

The problem statement is missing, so there isn’t enough information to reliably reconstruct what Codeforces 102979B (“Best Meeting Places”) is asking.

codeforcescompetitive-programming
CF 102980B - Поврежденный пароль

Let $mathcal{A}$ be a set of $t$-combinations and let $ $$kappat N = min{ where $partial mathcal{A}$ is the set of all $(t-1)$-subsets obtained by deleting one element from a member of $mathcal{A}$.

codeforcescompetitive-programming
CF 102980A - Обезвреживание бомбы

Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.

codeforcescompetitive-programming
CF 102980D - Побег из здания

I’m missing the actual statement for Codeforces 102980D - “Побег из здания”, so I can’t reconstruct the problem logic or write a correct editorial yet.

codeforcescompetitive-programming
CF 102980C - Кибер-взлом

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 102980C - Кибер-взлом” (Cyber-hack) isn’t included in your prompt, and I shouldn’t guess the task since even small misinterpretations would completely…

codeforcescompetitive-programming
CF 102984J - Setting Maps

The problem statement for Codeforces 102984J - Setting Maps is missing from your prompt, so there is no way to correctly reconstruct the solution, constraints, or intended algorithm.

codeforcescompetitive-programming
CF 102984B - Koosaga's Problem

Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.

codeforcescompetitive-programming
CF 102984K - Determinant

I can’t reliably write an editorial for this yet because the actual problem statement is missing. “Codeforces 102984K - Determinant” is just a title here, and different determinant problems on Codeforces vary a lot in structure, even if they share the same name.

codeforcescompetitive-programming
CF 102984I - Selecting Points and Segments

I don’t have the actual statement of Codeforces 102984I - Selecting Points and Segments, and without it I’d be forced to invent the problem structure, which would make the editorial meaningless or incorrect.

codeforcescompetitive-programming
CF 102984H - Stone Catch Game

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 102984H - Stone Catch Game is missing.

codeforcescompetitive-programming
CF 102984G - Solo Tree Game

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title, “Solo Tree Game,” but there’s no information about what the tree game rules are, what inputs are given, or what needs to be computed.

codeforcescompetitive-programming
CF 102984F - Rhythm Game

I can’t reliably write a correct Codeforces editorial here because the actual problem statement for 102984F - Rhythm Game is missing from your prompt.

codeforcescompetitive-programming
CF 102984E - Observer Game

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now we only have the title “Observer Game”, but no description of the rules, inputs, or outputs.

codeforcescompetitive-programming
CF 102984D - Non-Decreasing Subarray Game

The problem statement isn’t included, so I can’t reliably reconstruct the task or produce a correct editorial. “Non-Decreasing Subarray Game” could correspond to multiple different CF-style mechanics (range queries, segment operations, game DP, etc.

codeforcescompetitive-programming
CF 102984C - Gardening Game

We are given an $N times N$ grid of unit cells, all starting with beauty value zero. The system evolves through three kinds of operations applied over time. First, we may introduce horizontal or vertical cut lines across the grid.

codeforcescompetitive-programming
CF 102984A - Mango

I can’t produce a correct editorial for “Codeforces 102984A - Mango” yet because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 102985G - Expected Distance

Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 98

Let $[n]={1,2,\dots,n}$.

taocpmathematicsalgorithmsvolume-4hard
CF 102985J - Chang's Capricious Cupcakes

Let $T(m1,ldots,m{n-1})$ be the $(n-1)$-dimensional torus with cross order $preceq$, and let $x = x1cdots x{n-1}$ be the $N$th element of this torus in cross order. Let $T(m1,ldots,m{n-1},m)$ be the extended torus.

codeforcescompetitive-programming
CF 102985K - Verbose sandViches

I can’t write a correct editorial for this yet because the actual problem content is missing. Right now I only see the title “Verbose sandViches”, but no description of the task, input format, or output requirements.

codeforcescompetitive-programming
CF 102985I - Sharing Cereal II

I can’t write a correct editorial for “Codeforces 102985I - Sharing Cereal II” yet because the problem statement is missing from your prompt. Right now I have no information about: - what the input represents (arrays, graph, queries, etc.

codeforcescompetitive-programming
CF 102985E - Food Donations

Let $alpha$ be a $t$-combination, so $alpha$ is a $t$-element subset of ${0,1,dots,n-1}$. The operator $partialt alpha$ produces all $(t-1)$-combinations obtained by deleting one element of $alpha$. If $alpha={ct,dots,c1}$, then $$partialt alpha={alphasetminus{cj}mid 1le jle t}.

codeforcescompetitive-programming
CF 102985H - Coprime Ribs

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 102985H - Coprime Ribs” isn’t a standard publicly known problem in a way I can reliably reconstruct, and without the statement I would be guessing the entire…

codeforcescompetitive-programming
CF 102985F - Norman's N&N's

I can’t write a correct editorial for “Codeforces 102985F - Norman’s N&N’s” because the actual problem statement is missing.

codeforcescompetitive-programming
CF 102985D - Peter Piper Picked the Perfect Piece of Pizza

We are given a rectangular pizza placed on a coordinate plane. The bottom-left corner can be thought of as the origin, and the pizza spans a width and height. The chef then makes a set of horizontal cuts and a set of vertical cuts.

codeforcescompetitive-programming
CF 102985C - Spice Ratios

I can absolutely write this editorial in your required Codeforces style, but I’m missing the most important ingredient: the actual problem statement.

codeforcescompetitive-programming
CF 102986B - Sharing Cheerios

Let $alpha$ be a $t$-combination, so $alpha$ is a $t$-element subset of ${0,1,dots,n-1}$. The operator $partialt alpha$ produces all $(t-1)$-combinations obtained by deleting one element of $alpha$. If $alpha={ct,dots,c1}$, then $$partialt alpha={alphasetminus{cj}mid 1le jle t}.

codeforcescompetitive-programming
CF 102986H - Coprime Ribs

I don’t have the actual statement for Codeforces 102986H - Coprime Ribs in your prompt, so I can’t reliably reconstruct the problem or write a correct editorial.

codeforcescompetitive-programming
CF 102986G - Expected Distance

We start with a single node and then add nodes one by one. When node i is added, it attaches to one of the previous nodes j with probability proportional to a given weight aj. Once the parent j is chosen, the edge length between i and j is defined as ci + cj.

codeforcescompetitive-programming
CF 102986F - Norman's N&N's

I’m missing the actual problem statement for Codeforces 102986F - Norman’s N&N’s, so I can’t reliably reconstruct the solution or write a correct editorial.

codeforcescompetitive-programming
CF 102986D - Peter Piper Picked the Perfect Piece of Pizza

I’m missing the actual problem statement for Codeforces 102986D - Peter Piper Picked the Perfect Piece of Pizza, so I can’t safely reconstruct the intended model, constraints, or solution.

codeforcescompetitive-programming
CF 102986E - Food Donations

The prompt is missing the actual problem content. Right now we only have the title “Codeforces 102986E - Food Donations” but no description, input, output, or constraints.

codeforcescompetitive-programming
CF 102986A - Favorite Foods

The problem describes a person who has a list of favorite foods and is given a sequence of foods they eat over time.

codeforcescompetitive-programming
CF 102986C - Spice Ratios

I can’t reliably write a correct editorial for Codeforces 102986C - Spice Ratios without the actual problem statement.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 97

Let $C$ be a simplicial complex on a fixed vertex set $V$ with $|V|=4$.

taocpmathematicsalgorithmsvolume-4math-hard
CF 102992F - Fireworks

We are modeling a situation where a person repeatedly produces probabilistic “fireworks batches” over time. Each production attempt takes a fixed amount of time, and each produced firework independently has a small probability of being “perfect”.

codeforcescompetitive-programming
CF 102992E - Evil Coordinate

We are building a walk on an infinite grid starting from the origin. Each move is one unit in one of the four cardinal directions: right, left, up, or down, with given available counts for each direction. The final walk must use exactly all moves.

codeforcescompetitive-programming
CF 102993J - Pointer Analysis

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “Pointer Analysis”, but nothing about: what the input contains, what transformations are performed, or what needs to be computed.

codeforcescompetitive-programming
CF 102993I - Valuable Forests

The problem statement is missing from your prompt, so there’s no way to correctly derive the solution, constraints, or algorithmic structure for “Codeforces 102993I - Valuable Forests”.

codeforcescompetitive-programming
CF 102993A - Social Distancing

Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.

codeforcescompetitive-programming
CF 102993H - Dividing

I can’t write a correct Codeforces editorial without the actual problem statement. Right now, the prompt only includes the template, but “Dividing” (102993H) itself is missing, so there’s no way to know: - what is being divided (arrays, numbers, graph components, etc.

codeforcescompetitive-programming
CF 102993G - Topo Counting

I don’t have the actual statement for Codeforces 102993G - Topo Counting in your message, so I can’t reliably reconstruct the problem, constraints, or intended solution path.

codeforcescompetitive-programming
CF 102993F - Tokens on the Tree

The editorial can’t be written yet because the actual problem statement for Codeforces 102993F - Tokens on the Tree is missing.

codeforcescompetitive-programming
CF 102993E - NeoMole Synthesis

The problem statement is missing from your prompt, so I can’t reliably reconstruct the task or write a correct Codeforces-style editorial.

codeforcescompetitive-programming
CF 102993D - Fake News

I can’t reliably reconstruct the full problem from just the name and ID, and for a Codeforces editorial that would mean guessing the core task, which would make the entire solution and correctness discussion meaningless.

codeforcescompetitive-programming
CF 102993B - Mask Allocation

The problem statement for Codeforces 102993B - Mask Allocation is missing from your prompt, so there is no way to reconstruct the logic, constraints, or intended algorithm correctly.

codeforcescompetitive-programming
CF 102993C - A National Pandemic

The problem statement section is empty, so there isn’t enough information to reconstruct what “A National Pandemic” is actually asking.

codeforcescompetitive-programming
CF 102994D - String Theory

Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.

codeforcescompetitive-programming
CF 102994I - A Math Problem

Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.

codeforcescompetitive-programming
CF 102994M - Travel Dream

I can’t produce a correct editorial yet because the actual problem statement for Codeforces 102994M - Travel Dream is missing from your prompt.

codeforcescompetitive-programming
CF 102994L - Landlord

I can’t reliably write a correct Codeforces editorial for “102994L - Landlord” because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 102994K - Data Structure

I can’t reliably write an editorial for “Codeforces 102994K - Data Structure” because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 102994J - Gaokao

I can’t produce a correct Codeforces-style editorial yet because the actual problem content for 102994J - Gaokao is missing from your prompt.

codeforcescompetitive-programming
CF 102994H - Yet Another Geometry Problem

The problem statement is missing from your prompt, so I can’t reliably reconstruct what Codeforces 102994H is asking. For a geometry problem especially, the entire solution structure depends on very specific details (points, segments, distances, queries, constraints).

codeforcescompetitive-programming
CF 102994C - An Unsure Catch

Let $n=s+t$ as in (1), and let an $(s,t)$-combination be written in the form $ct cdots c2 c1$ satisfying (3), that is $n ct cdots c2 c1 ge 0.

codeforcescompetitive-programming
CF 102994G - Blackjack

I can’t reliably write a correct Codeforces 102994G editorial from what you’ve provided because the actual problem content (rules of “Blackjack”, input format, and required output) is missing.

codeforcescompetitive-programming
CF 102994F - Girlfriend

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 102994F - Girlfriend is missing from your prompt. Right now I only see the template sections (Input/Output are empty), which isn’t enough to reconstruct the problem.

codeforcescompetitive-programming
CF 102994E - Road Construction

I can’t reliably write a correct editorial for Codeforces 102994E - Road Construction without the actual problem statement.

codeforcescompetitive-programming
CF 102994B - Gifted Composer

I can’t responsibly write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “102994B - Gifted Composer”, but no description of what the input represents, what is being optimized or computed, or even the…

codeforcescompetitive-programming
CF 102994A - Everyone Loves Playing Games

I’m missing the actual problem statement for Codeforces 102994A - Everyone Loves Playing Games, so I can’t reliably reconstruct the task or derive the correct algorithm.

codeforcescompetitive-programming
CF 103003D - Set of Points

Let $n=s+t$ as in (1), and let an $(s,t)$-combination be written in the form $ct cdots c2 c1$ satisfying (3), that is $n ct cdots c2 c1 ge 0.

codeforcescompetitive-programming
CF 103003E - Dream and the Multiverse

I can’t reliably write a correct editorial for Codeforces 103003E - Dream and the Multiverse because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 103003A - Modular Exponentiation

The problem statement section is empty, so there’s not enough information to write a correct editorial. “Modular Exponentiation” could mean several different tasks on Codeforces: single query fast power computation, multiple queries with different moduli, precomputation…

codeforcescompetitive-programming
CF 103003B - DDDFT

I can’t write a correct Codeforces editorial for 103003B - DDDFT yet because the actual problem statement is missing. Right now I don’t know: - what the input represents, - what transformation or computation is required, - or what the output should be.

codeforcescompetitive-programming
CF 103029B - John, Katya

The exercise refers to the “basic compression lemma (85)”, but the statement of (85) is not included in the provided excerpt of Section 7.2.1.3.

codeforcescompetitive-programming
CF 103029D - John and pizza

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103029D - John and pizza” isn’t enough on its own to reconstruct the task reliably, and guessing would almost certainly produce a wrong solution and misleading…

codeforcescompetitive-programming
CF 103029C - John, Katya, no nuts

I can’t produce a correct editorial for this problem yet because the actual problem statement is missing. “Codeforces 103029C - John, Katya, no nuts” doesn’t include any description of the input/output or the task, and without that there’s nothing concrete to restate…

codeforcescompetitive-programming
CF 103029A - John and nuts

I’m missing the actual problem statement for Codeforces 103029A - John and nuts in your prompt, so I can’t safely reconstruct the intended solution or write a correct editorial.

codeforcescompetitive-programming
CF 103031A - Подсчет хештегов

The problem statement is missing, so I can’t reliably reconstruct what “Подсчет хештегов” (Hashtag counting) is asking for or what the required output format is.

codeforcescompetitive-programming
CF 103031C - Шестизначные документы

The exercise refers to the “basic compression lemma (85)”, but the statement of (85) is not included in the provided excerpt of Section 7.2.1.3.

codeforcescompetitive-programming
CF 103031E - Загадочное устройство

The problem statement for Codeforces 103031E - “Загадочное устройство” is missing from your prompt, so I don’t have the actual rules, inputs, or required output to base an editorial on.

codeforcescompetitive-programming
CF 103031D - Government Census

I don’t have the actual problem statement for Codeforces 103031D - Government Census in your message, and I can’t reliably reconstruct it from the ID alone without risking inventing details.

codeforcescompetitive-programming
CF 103031B - Arranging Utensils

I can’t write a correct editorial yet because the actual problem statement (including input format, constraints, and what “Arranging Utensils” is asking) is missing from your prompt.

codeforcescompetitive-programming
CF 103034B - As Easy As ABC

Let configurations be binary strings $a{n-1}dots a1 a0$ with exactly $t$ ones, with the constraint $a0 = 0$. Let $V(n,t)$ denote this set.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 96

Let F_n(z)=\prod_{j=0}^{n-1}(1+z+\cdots+z^{s_j}), so that

taocpmathematicsalgorithmsvolume-4math-medium
CF 103036G - Scale Goodness

We are given a permutation of the integers from 1 to n, and we simulate processing it from left to right. At each step, we look only at the values that have already appeared before the current position.

codeforcescompetitive-programming
CF 103036B - Vinyl Records

Let a canonical basis $(alpha1,ldots,alphat)$ be represented as an ordered $t$-tuple of distinct elements of ${1,ldots,n}$. This is equivalent to a permutation of $t$ distinct symbols chosen from $n$, with order preserved.

codeforcescompetitive-programming
CF 103036F - Ice-T

I don’t have the actual problem statement for Codeforces 103036F - Ice-T in your message, and I can’t reliably reconstruct it from the title alone without risking inventing details.

codeforcescompetitive-programming
CF 103036E - Algo's Rhythm

We are given a musical composition problem where a song is built by placing notes end to end until a fixed total duration is reached. Each note has a positive integer length, and we can reuse notes any number of times.

codeforcescompetitive-programming
CF 103036D - Melodic Harmonies II

I can’t write a correct Codeforces editorial for 103036D - Melodic Harmonies II without the actual problem statement. Right now the statement section is empty, so there’s no way to determine: - what the input represents (arrays, graph, music structure, etc.

codeforcescompetitive-programming
CF 103036C - Melodic Harmonies I

I can’t reliably write a correct editorial for this without the actual problem statement. “Codeforces 103036C - Melodic Harmonies I” is not enough on its own, and I don’t have the input/output rules, constraints, or the intended structure of the task.

codeforcescompetitive-programming
CF 103036A - Switching Up the Playlist

I don’t have the actual statement for Codeforces 103036A - Switching Up the Playlist, so I can’t reconstruct the problem meaningfully yet.

codeforcescompetitive-programming
CF 103037F - Ice-T

Let a canonical basis $(alpha1,ldots,alphat)$ be represented as an ordered $t$-tuple of distinct elements of ${1,ldots,n}$. This is equivalent to a permutation of $t$ distinct symbols chosen from $n$, with order preserved.

codeforcescompetitive-programming
CF 103037H - Symphony

Let a canonical basis $(alpha1,ldots,alphat)$ be represented as an ordered $t$-tuple of distinct elements of ${1,ldots,n}$. This is equivalent to a permutation of $t$ distinct symbols chosen from $n$, with order preserved.

codeforcescompetitive-programming
CF 103037J - Bohemian Rhapsody

I can’t reliably reconstruct a correct editorial yet because the full problem statement for Codeforces 103037J - Bohemian Rhapsody is missing from your prompt, and I don’t want to hallucinate the task or give you a misleading solution.

codeforcescompetitive-programming
CF 103037I - Creati

I’m missing the actual problem statement for Codeforces 103037I - Creati, so I can’t produce a correct editorial yet without guessing the core task.

codeforcescompetitive-programming
CF 103037G - Scale Goodness

I can’t reliably write a correct Codeforces editorial for 103037G - Scale Goodness without the actual problem statement.

codeforcescompetitive-programming
CF 103037D - Melodic Harmonies II

Let a canonical basis $(alpha1,ldots,alphat)$ be represented as an ordered $t$-tuple of distinct elements of ${1,ldots,n}$. This is equivalent to a permutation of $t$ distinct symbols chosen from $n$, with order preserved.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 95

Let $U$ denote the set of all multicombinations under consideration in Corollary C, represented in the form $c_4c_3c_2c_1$ with $3 \ge c_4 \ge c_3 \ge c_2 \ge c_1 \ge 0.$ The hint specifies that withi...

taocpmathematicsalgorithmsvolume-4medium
CF 103037E - Algo's Rhythm

The problem statement is missing, so there is not enough information to write a correct or meaningful editorial. Right now, we only know the title “Algo’s Rhythm”, but there is no description of the input, output, constraints, or what the algorithmic task actually is.

codeforcescompetitive-programming
CF 103037C - Melodic Harmonies I

I’m missing the actual problem statement for Codeforces 103037C - Melodic Harmonies I, so I can’t reliably reconstruct the task or derive a correct solution.

codeforcescompetitive-programming
CF 103048H - Histogram in 3D

Codeforces 103048H: Histogram in 3D

codeforcescompetitive-programming
CF 103048K - K-Primes

I can’t write a correct editorial yet because the actual problem statement for CF 103048K - K-Primes isn’t included in your message.

codeforcescompetitive-programming