brain

tamnd's digital brain — notes, problems, research

43815 notes

CF 103110I - Grid Shuffling

The problem statement for “103110I - Grid Shuffling” is missing from your prompt, so I don’t have the actual rules of the task (what “shuffling” means, what operations are allowed, or what needs to be computed).

codeforcescompetitive-programming
CF 103110H - Street Layout

I can’t write a correct editorial for this yet because the actual problem content for Codeforces 103110H - Street Layout isn’t included in your prompt.

codeforcescompetitive-programming
CF 103110F - Island Isolation

I don’t have the actual problem statement for Codeforces 103110F - Island Isolation, so I can’t safely write a correct editorial yet.

codeforcescompetitive-programming
CF 103110G - Map Matching

I don’t have the actual statement of Codeforces 103110G - Map Matching, and without it I can’t reliably reconstruct the problem or write a correct editorial.

codeforcescompetitive-programming
CF 103110D - Apple Orchard

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 103110D - Apple Orchard is missing from your prompt.

codeforcescompetitive-programming
CF 103110C - Reverse Race

I can’t write a correct editorial yet because the actual problem statement is missing. Right now I only see the title “103110C - Reverse Race”, but no description of what the race rules are, what the input represents, or what needs to be computed.

codeforcescompetitive-programming
CF 103110A - Mountain Climbing

Let $n = s + t$. A Chase sequence $C{st}$ is a Gray-code ordering of all $(s,t)$-combinations, in which successive combinations differ by a single unit transfer of a $1$ across a contiguous block of $0$s in the binary representation, equivalently by updating the list…

codeforcescompetitive-programming
CF 103110B - Digit Sum

I’m missing the actual problem statement for “Codeforces 103110B - Digit Sum”, so I can’t reconstruct the intended task or derive a correct solution.

codeforcescompetitive-programming
CF 103112B - Клавиатура

Let $n = s + t$. A Chase sequence $C{st}$ is a Gray-code ordering of all $(s,t)$-combinations, in which successive combinations differ by a single unit transfer of a $1$ across a contiguous block of $0$s in the binary representation, equivalently by updating the list…

codeforcescompetitive-programming
CF 103112G - Квест

The editorial request is missing the only thing that actually determines the solution: the problem statement. “Codeforces 103112G - Квест” is not enough to reconstruct the task reliably, and guessing would almost certainly produce a wrong or irrelevant editorial.

codeforcescompetitive-programming
CF 103112F - Солдатская смекалка

I can write the full Codeforces-style editorial, but the problem statement for 103112F - “Солдатская смекалка” is missing from your message.

codeforcescompetitive-programming
CF 103112E - Фокусы

I don’t have the actual statement of Codeforces 103112E - Фокусы in your prompt, and without it I can’t reliably reconstruct the problem or produce a correct editorial.

codeforcescompetitive-programming
CF 103112D - Монеты для друзей

I can’t write a correct editorial yet because the actual problem statement for “103112D - Монеты для друзей” is missing from your prompt.

codeforcescompetitive-programming
CF 103112A - Номер сундука

I can’t write a correct editorial for this yet because the actual problem statement (what the “chest number” means, what the input describes, and what is required in the output) is missing.

codeforcescompetitive-programming
CF 103112C - Надпись

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 103112C - “Надпись” is missing from your prompt. Right now, I don’t know what the input represents, what transformations are allowed, or what needs to be computed.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 72

Theorem W is proved in Section 7.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.3 Exercise 71

Let $G$ be a simple graph with $m=10^6$ edges, and let $K_t(G)$ denote the number of $t$-cliques in $G$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103114H - Hsueh- and Meeting

Let $mathcal{F}(N,t)$ denote a family of $N$ distinct $t$-combinations, and let $kappat(N)$ be the extremal quantity defined in Section 7.2.1.3, namely the minimum possible size of the derived family under the Kruskal-Katona construction used in Theorem K.

codeforcescompetitive-programming
CF 103114J - Jahaxiki's journey III - Tryna lost

We are given a grid-like planar map where movement happens between small square cells. Each cell is potentially connected to its neighboring cells through openings, while barriers are represented implicitly by wall characters in a textual layout.

codeforcescompetitive-programming
CF 103114I - Iahaxiki's journey II - enjoying

We are given a weighted tree with $n$ vertices. Each edge connects two vertices and has a positive length. The task is to choose a simple path in this tree such that the path contains exactly $k$ vertices, and among all such paths we want the one with the maximum possible…

codeforcescompetitive-programming
CF 103114G - Guess Permutation

We are given a hidden permutation of the numbers from 1 to n, stored across positions 1 to n. Our task is to recover the entire permutation, meaning we must determine the exact value at every position. The only way to obtain information is through queries.

codeforcescompetitive-programming
CF 103114F - Fstee1XD and Minioins

The process described in this problem is a deterministic population growth system where each individual has an age-dependent reproduction rule. We start with a single minion born on day one.

codeforcescompetitive-programming
CF 103114B - Bsueh- and Gold Medals

Let $mathcal{F}(N,t)$ denote a family of $N$ distinct $t$-combinations, and let $kappat(N)$ be the extremal quantity defined in Section 7.2.1.3, namely the minimum possible size of the derived family under the Kruskal-Katona construction used in Theorem K.

codeforcescompetitive-programming
CF 103114E - Ewo Slices of Bread with Cheese

We are given a collection of cheese pieces, each with an initial freshness value. Time advances in discrete days. Every day, all remaining pieces simultaneously lose one unit of freshness.

codeforcescompetitive-programming
CF 103114D - Dllllan and his friends

We are given a set of points on the plane, each representing a friend’s house. We need to choose a single point, interpreted as the location of a new home, and also compute a travel cost associated with visiting all friends from that home.

codeforcescompetitive-programming
CF 103114C - Chtholly and Floating Islands

We are given a line of numbered islands starting from island 1 up to island n. From any island j, Chtholly can jump forward by adding one value from a set of available “step sizes”, meaning she moves from j to j + x where x is chosen from her current ability list.

codeforcescompetitive-programming
CF 103114A - Aahaxiki's journey I - set off

The task describes a transportation network over a set of cities, where each city contains four internal “modes” of being: school, train station, airport, and competition site.

codeforcescompetitive-programming
CF 103115I - chino with mates

Let $mathcal{F}(N,t)$ denote a family of $N$ distinct $t$-combinations, and let $kappat(N)$ be the extremal quantity defined in Section 7.2.1.3, namely the minimum possible size of the derived family under the Kruskal-Katona construction used in Theorem K.

codeforcescompetitive-programming
CF 103115J - do NOT a=2b

I don’t have the actual statement for Codeforces 103115J - “do NOT a=2b” in the prompt you provided, so I can’t reliably reconstruct the problem or write a correct editorial without guessing.

codeforcescompetitive-programming
CF 103115K - chino with c language

I can’t write a correct editorial for “Codeforces 103115K - chino with c language” without the actual problem statement.

codeforcescompetitive-programming
CF 103115H - cocktail with pony

The problem statement is missing from your prompt, so there isn’t enough information to reconstruct what “cocktail with pony” is asking, let alone derive a correct algorithm or write a meaningful editorial.

codeforcescompetitive-programming
CF 103115E - is the order a rabbit ??

I can’t reliably write an editorial for Codeforces 103115E - “is the order a rabbit ??” without the actual problem statement.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 70

Let $\mathcal{A}$ be a set of $t$-combinations and let $|\mathcal{A}| = N$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103115A - chino with string

Let $mathcal{F}(N,t)$ denote a family of $N$ distinct $t$-combinations, and let $kappat(N)$ be the extremal quantity defined in Section 7.2.1.3, namely the minimum possible size of the derived family under the Kruskal-Katona construction used in Theorem K.

codeforcescompetitive-programming
CF 103115G - cocktail with snake

I don’t have the actual statement of Codeforces 103115G - “cocktail with snake”, so I can’t reliably reconstruct the problem, constraints, or intended solution path.

codeforcescompetitive-programming
CF 103115F - chino with ball

The problem statement is missing, so I can’t reconstruct the solution or write a correct editorial yet. Codeforces problem IDs alone aren’t enough because multiple problems (especially from unofficial or Gym rounds like 103115F) don’t have reliably accessible or unique…

codeforcescompetitive-programming
CF 103115D - cocktail with swap

I can write the full editorial in the exact format you requested, but I’m missing the actual problem statement for Codeforces 103115D - “cocktail with swap”.

codeforcescompetitive-programming
CF 103115B - cocktail with hearthstone

We are given a process that starts with a huge number of identical players, all located at a virtual state written as $(0,0)$. A state $(a,b)$ represents a player who has won $a$ games and lost $b$ games.

codeforcescompetitive-programming
CF 103115C - chino with minimum

I can’t reliably write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103115C - chino with minimum” doesn’t provide enough information on its own, and I shouldn’t guess the task, constraints, or required algorithm.

codeforcescompetitive-programming
CF 103117M - True Story

Let $kappat(N)$ denote the function defined in Section 7.2.1.3 via the combinatorial representation $$N = binom{nt}{t} + binom{n{t-1}}{t-1} + cdots + binom{n1}{1}, qquad nt n{t-1} cdots n1 ge 0,$$ and $$kappat(N) = binom{nt}{t-1} + binom{n{t-1}}{t-2} + cdots + binom{n1}{0}.

codeforcescompetitive-programming
CF 103117K - K-skip Permutation

The problem statement section is empty, so there isn’t enough information to reconstruct what “K-skip Permutation” actually asks or what the input/output constraints are.

codeforcescompetitive-programming
CF 103117L - Spicy Restaurant

The problem statement for 103117L - Spicy Restaurant is missing from your prompt, so I can’t reliably reconstruct the task or derive a correct solution. Right now, anything I write would be guesswork, and for a Codeforces editorial that would defeat the purpose of the exercise.

codeforcescompetitive-programming
CF 103117C - Ants

Let $kappat(N)$ denote the function defined in Section 7.2.1.3 via the combinatorial representation $$N = binom{nt}{t} + binom{n{t-1}}{t-1} + cdots + binom{n1}{1}, qquad nt n{t-1} cdots n1 ge 0,$$ and $$kappat(N) = binom{nt}{t-1} + binom{n{t-1}}{t-2} + cdots + binom{n1}{0}.

codeforcescompetitive-programming
CF 103117H - Nihongo wa Muzukashii Desu

The problem statement for Codeforces 103117H - “Nihongo wa Muzukashii Desu” is missing from your prompt, so I don’t have the actual task definition, inputs, or required output to build a correct editorial.

codeforcescompetitive-programming
CF 103117G - Hourly Coding Problem

I don’t have the actual problem statement for Codeforces 103117G - Hourly Coding Problem in your message, and I can’t reliably infer it from the title alone without risking making up details.

codeforcescompetitive-programming
CF 103117E - Don't Really Like How The Story Ends

We are given a graph with n vertices and some existing undirected edges. Alongside this, we are given a permutation of the vertices, which represents the exact order in which a DFS, started from the first vertex in that permutation, originally discovered nodes.

codeforcescompetitive-programming
CF 103117F - Direction Setting

I don’t have the actual statement of Codeforces 103117F - Direction Setting in your prompt, so I can’t reliably reconstruct the problem or produce a correct editorial without risking inventing details.

codeforcescompetitive-programming
CF 103117D - Rock Paper Scissors

I can write the full Codeforces-style editorial, but the problem statement for 103117D - Rock Paper Scissors is missing from your prompt. Right now I only know the title, which isn’t enough to reconstruct the rules reliably.

codeforcescompetitive-programming
CF 103117B - Hotpot

We are simulating a turn-based process over a circular group of participants. Each participant is associated with a fixed ingredient type. A global multiset called the pot evolves over time.

codeforcescompetitive-programming
CF 103117A - Chuanpai

The problem statement for Codeforces 103117A - Chuanpai is missing from your prompt, so I don’t have the actual rules, input format, or task definition needed to write a correct editorial.

codeforcescompetitive-programming
CF 103118L - Construction of 5G Base Stations

Let $kappat(N)$ denote the function defined in Section 7.2.1.3 via the combinatorial representation $$N = binom{nt}{t} + binom{n{t-1}}{t-1} + cdots + binom{n1}{1}, qquad nt n{t-1} cdots n1 ge 0,$$ and $$kappat(N) = binom{nt}{t-1} + binom{n{t-1}}{t-2} + cdots + binom{n1}{0}.

codeforcescompetitive-programming
CF 103118M - Matrix Problem

I can’t write a correct editorial yet because the actual problem statement (operations, constraints, and what “Matrix Problem” asks for) is missing.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 69

Let $A$ be a set of $t$-combinations of ${0,1,\dots,n-1}$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103118J - Tuition Agent

We are given a set of clients, each with a distinct rank value. For every client, we must make a binary decision: either invest money to train them into a tutor, or invest money to turn them into a student who will receive tutoring.

codeforcescompetitive-programming
CF 103118K - Piggy Calculator

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title “Piggy Calculator”, but there is no description of what the calculator does, what inputs look like, or what needs to be computed.

codeforcescompetitive-programming
CF 103118B - Build Roads

Let $kappat(N)$ denote the function defined in Section 7.2.1.3 via the combinatorial representation $$N = binom{nt}{t} + binom{n{t-1}}{t-1} + cdots + binom{n1}{1}, qquad nt n{t-1} cdots n1 ge 0,$$ and $$kappat(N) = binom{nt}{t-1} + binom{n{t-1}}{t-2} + cdots + binom{n1}{0}.

codeforcescompetitive-programming
CF 103118I - Chemical Code

I’m missing the actual statement of Codeforces 103118I - Chemical Code, so I can’t safely derive the solution or write a correct editorial without guessing the problem details. Please paste the full problem statement (or even a screenshot/text dump).

codeforcescompetitive-programming
CF 103118H - Adventurer's Guild

I can’t produce a correct editorial for Codeforces 103118H - Adventurer’s Guild because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 103118G - Grade Point Average

I cannot write a correct editorial yet because the problem statement is missing from your prompt, and “Grade Point Average” on Codeforces Gym 103118G has multiple different interpretations depending on the exact rounding rule and constraints.

codeforcescompetitive-programming
CF 103118F - Birthday Cake

I can’t produce a correct, meaningful editorial for “Codeforces 103118F - Birthday Cake” yet because the problem statement is missing from your prompt. Right now, I only see the header and empty “Problem Statement / Input / Output” sections.

codeforcescompetitive-programming
CF 103118E - Evaluate Expression

The problem statement is missing from your message, so there’s no way to reconstruct the intended operations, constraints, or required evaluation rules for “103118E - Evaluate Expression”.

codeforcescompetitive-programming
CF 103118D - Dyson Box

I can’t reliably write a correct Codeforces editorial here because the problem statement is missing. “103118D - Dyson Box” isn’t included in your prompt, so anything I produce would be guesswork.

codeforcescompetitive-programming
CF 103118A - Beta Go

I can’t write a correct editorial yet because the actual problem statement for Codeforces 103118A - Beta Go is missing from your message.

codeforcescompetitive-programming
CF 103118C - Cat Virus

The problem statement section is empty, so there isn’t enough information to reconstruct what “Cat Virus” is actually asking or what the input/output represent.

codeforcescompetitive-programming
CF 103119L - Random Permutation

We are generating a random upper bound array of size $n$, where each entry $ai$ is chosen independently and uniformly from the integers $1$ to $n$.

codeforcescompetitive-programming
CF 103119K - Candy Ads

We are given a set of rectangular advertisements, each one active only during a time interval and occupying a fixed axis-aligned rectangle on a discrete grid. Each ad is therefore a space-time object: a rectangle in 2D space that exists across a contiguous range of days.

codeforcescompetitive-programming
CF 103119J - Jewel Grab

We are given a row of jewels indexed from left to right. Each position contains a jewel with a color and a value. The colors are arbitrary integers, and values are large positive numbers. We process two types of operations.

codeforcescompetitive-programming
CF 103119H - Fly Me To The Moon

We are working on a huge directed system of “stations” placed on every integer coordinate point in a 1000 by 1000 grid, except for the origin and the destination. The journey starts at (0, 0) and must end at (1000, 1000).

codeforcescompetitive-programming
CF 103119G - Game on Sequence

We are given a growing sequence of numbers, where each number is between 0 and 255, so every value fits in 8 bits. After each update, we may be asked to start a two-player game from a given position in the sequence. From a starting index k, a token sits on position k.

codeforcescompetitive-programming
CF 103119F - Fixing Networks

We are asked to construct an undirected simple graph on $n$ labeled vertices. Every vertex must have exactly degree $d$, meaning each station is connected to exactly $d$ other stations. Self-loops and multiple edges are forbidden, so this is a standard simple $d$-regular graph.

codeforcescompetitive-programming
CF 103119E - Mountain

The mountain is a polygonal terrain formed by connecting points from left to right, starting at ground level, rising through given heights, and then returning back to ground.

codeforcescompetitive-programming
CF 103119A - Accelerator

We are given a sequence of accelerators, each carrying a multiplicative factor. A spaceship starts with velocity zero and passes through all accelerators in some order.

codeforcescompetitive-programming
CF 103119C - Club Assignment

We are given several independent test cases. In each test case, there are $n$ students, and each student has a single integer attribute $wi$. We must split these students into two clubs, labeled 1 and 2.

codeforcescompetitive-programming
CF 103134A - Kobus hates sweepstakes

Let $kappat(N)$ denote the function defined in Section 7.2.1.3 via the combinatorial representation $$N = binom{nt}{t} + binom{n{t-1}}{t-1} + cdots + binom{n1}{1}, qquad nt n{t-1} cdots n1 ge 0,$$ and $$kappat(N) = binom{nt}{t-1} + binom{n{t-1}}{t-2} + cdots + binom{n1}{0}.

codeforcescompetitive-programming
CF 103134J - Raphael singer

The problem statement is missing from your prompt, so there isn’t enough information to write a correct editorial. “Codeforces 103134J - Raphael singer” doesn’t provide any recoverable structure on its own, and guessing would lead to an incorrect solution write-up.

codeforcescompetitive-programming
CF 103134I - Competitive Mario Kart

I don’t have the actual statement of Codeforces 103134I - Competitive Mario Kart in your prompt (the “Problem Statement / Input / Output” sections are empty), so I can’t reliably reconstruct the rules, constraints, or required output.

codeforcescompetitive-programming
CF 103134H - The comedian Nathan

The problem statement is missing from your message, so I don’t have the actual task definition, input/output format, or constraints for Codeforces 103134H - The comedian Nathan.

codeforcescompetitive-programming
CF 103134G - The blut dot game

I can’t write a correct editorial for this yet because the actual problem content is missing. Right now I only have the title “The blut dot game”, but no rules, no input/output format, and no constraints.

codeforcescompetitive-programming
CF 103134F - Confusing Morete

I’m missing the actual problem statement for Codeforces 103134F - Confusing Morete, so I can’t responsibly write a correct editorial yet.

codeforcescompetitive-programming
CF 103134D - Corona Mashup

We are given a set of participants, each of whom becomes available starting from a certain day and remains available for every day after that forever.

codeforcescompetitive-programming
CF 103134E - Learning new languages

I can’t produce a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103134E - Learning new languages” is not enough to reconstruct the task reliably, and guessing would very likely lead to a wrong solution and misleading…

codeforcescompetitive-programming
CF 103134B - Guidi wants to be stronger

I don’t have the actual statement of Codeforces 103134B - “Guidi wants to be stronger”, and without it I’d be forced to guess the problem structure, which would make the editorial meaningless or incorrect.

codeforcescompetitive-programming
CF 103134C - Harada and the lucky numbers

I can’t write a correct editorial without the actual problem statement. Right now, only the title is available (“Harada and the lucky numbers”), but the input/output definitions, constraints, and what needs to be computed are missing.

codeforcescompetitive-programming
CF 103136A - Буфет

Let a string $alpha$ consist of symbols from ${+, -, 0}$ with exactly $t$ zeros and $s$ signs, where each nonzero symbol is either $+$ or $-$. An R-block is a substring of the form $-^k+$, $k ge 0$, that is immediately preceded by $0$ and not followed by $-$.

codeforcescompetitive-programming
CF 103136I - Разделение труда

The problem statement section is empty, so there isn’t enough information to write a correct editorial yet. Codeforces 103136I “Разделение труда” could refer to a specific task, but without the actual description, constraints, or samples, any solution I…

codeforcescompetitive-programming
CF 103136H - По тарелочкам

The problem statement is missing from your prompt, so there’s no way to reconstruct a correct editorial without guessing the task.

codeforcescompetitive-programming
CF 103136G - Шахматный турнир

I don’t have the actual statement of Codeforces 103136G - “Шахматный турнир”, so I can’t responsibly write a correct editorial yet.

codeforcescompetitive-programming
CF 103136F - Все дороги ведут в ПГУ

The problem statement section is empty, so there isn’t enough information to reconstruct the task. For Codeforces editorials, I need at least the full statement (or a screenshot / text of it), because everything downstream depends on the exact graph structure, operations, or…

codeforcescompetitive-programming
CF 103136E - Why is calculator needed for?

I can’t write a correct editorial yet because the actual problem statement for “Codeforces 103136E - Why is calculator needed for?” is missing from your prompt.

codeforcescompetitive-programming
CF 103136D - Длинные руки

The problem statement is missing from your prompt, so I don’t have the actual rules, input format, or required computation for Codeforces 103136D - “Длинные руки”.

codeforcescompetitive-programming
CF 103136C - Магазин дешевых вещей

I’m missing the actual problem statement for Codeforces 103136C - “Магазин дешевых вещей”, so I can’t reliably reconstruct the intended algorithm or constraints from the name alone.

codeforcescompetitive-programming
CF 103136B - PSU

The problem statement is missing from your prompt, so I can’t reconstruct the task or derive a correct algorithm for Codeforces 103136B - PSU. To write a proper editorial in the style you requested, I need at least one of the following: 1.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 68

Let $\alpha$ be a $t$-combination, so $\alpha$ is a $t$-element subset of ${0,1,\dots,n-1}$.

taocpmathematicsalgorithmsvolume-4math-simple
CF 103150G - Segmentation Fault

Let a string $alpha$ consist of symbols from ${+, -, 0}$ with exactly $t$ zeros and $s$ signs, where each nonzero symbol is either $+$ or $-$. An R-block is a substring of the form $-^k+$, $k ge 0$, that is immediately preceded by $0$ and not followed by $-$.

codeforcescompetitive-programming
CF 103150I - X-OR XOR

I don’t have the actual statement for Codeforces 103150I “X-OR XOR”, so I can’t safely derive a correct editorial yet. With XOR-style problems especially, small missing details completely change the intended solution (range vs. prefix, updates vs.

codeforcescompetitive-programming
CF 103150H - William Tell

The problem section is empty, so there isn’t enough information to write a correct editorial. For a Codeforces editorial, I need at least the full statement (or at minimum: input format, output format, constraints, and a description of the task).

codeforcescompetitive-programming
CF 103150F - Palindromicity

I can write the full editorial in the exact style you want, but I’m missing the only thing that makes it possible: the actual problem statement.

codeforcescompetitive-programming
CF 103150E - o

I can’t reliably write a correct editorial for this yet because the actual problem statement is missing. Right now I only see “Codeforces 103150E - o” with empty input/output sections, which isn’t enough to reconstruct the task.

codeforcescompetitive-programming
CF 103150B - Arrowing Process

Let κt(N) be the leading parameter in the degree-$t$ combinatorial representation of $N$, so that κt(N) is the unique integer $nt$ satisfying $$binom{nt}{t} le N < binom{nt+1}{t}.

codeforcescompetitive-programming
CF 103150D - Moving Points

I’m missing the actual problem statement for Codeforces 103150D - Moving Points in your prompt. Right now the “Problem Statement / Input / Output” sections are empty, so I don’t have enough information to: - understand what is being computed, - derive the algorithm, - or…

codeforcescompetitive-programming