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tamnd's digital brain — notes, problems, research

41570 notes

CF 103075G - Рудольф и лампочки

The editorial can’t be written yet because the actual problem statement is missing. Right now I only know the title “Рудольф и лампочки”, but not what the lamps model, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
CF 103075F - Рудольф и дорога в университет

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the title and metadata (“Рудольф и дорога в университет”), but no description of the road, constraints, input format, or required…

codeforcescompetitive-programming
CF 103075D - Рудольф и логическая схема

I’m missing the actual problem statement for Codeforces 103075D - “Рудольф и логическая схема”, so I can’t reliably reconstruct the intended solution or write a correct editorial yet.

codeforcescompetitive-programming
CF 103075E - Рудольф и файловая система

The problem statement is missing from the prompt, so I can’t correctly reconstruct the solution, constraints, or edge cases for Codeforces 103075E. For this kind of editorial, I need at least the full statement or a link content (input/output description and constraints).

codeforcescompetitive-programming
CF 103075B - Рудольф и диагональный сканер

I can’t reliably write a correct Codeforces editorial here because the actual problem statement is missing. Right now, all I have is the title “Рудольф и диагональный сканер”, but no description of the grid, operations, or required output.

codeforcescompetitive-programming
CF 103075C - Рудольф и полином

I don’t have the actual statement of Codeforces 103075C - “Рудольф и полином”, and without it I can’t safely reconstruct the problem or derive a correct solution.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 90

Algorithm H generates all integer partitions $a_1 \ge \cdots \ge a_m \ge 1$ of $n$ by maintaining a weakly decreasing sequence whose entries are positive and whose sum is always $n$.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.3 Exercise 89

Let the $2\times 2\times 3$ torus be the Cartesian product T = \mathbb{Z}_2 \times \mathbb{Z}_2 \times \mathbb{Z}_3, so each element is a triple $(x,y,z)$ with $x,y \in {0,1}$ and $z \in {0,1,2}$, wit...

taocpmathematicsalgorithmsvolume-4medium
CF 103098F - Friendship Circles

Let $X = a{n-1}a{n-2}cdots a0$ be the binary representation of an $(s,t)$-combination, so $sum ai = t$. Write its associated fencepost form as in equation (14), $$X = 0^{qt}1,0^{q{t-1}}1cdots 1,0^{q0},$$ where each $qi ge 0$ and $sum{i=0}^t qi = s$.

codeforcescompetitive-programming
CF 103098L - Long Grid Covering

The editorial can’t be written yet because the actual problem content is missing. Right now, “Codeforces 103098L - Long Grid Covering” has no statement, constraints, or examples provided in your prompt.

codeforcescompetitive-programming
CF 103098I - Interesting Scoring Systems

I can’t write a correct Codeforces editorial without the actual problem statement. Right now the “Problem Statement / Input / Output” sections are empty, and for a problem like 103098I - Interesting Scoring Systems, the solution depends entirely on the scoring rules and…

codeforcescompetitive-programming
CF 103098G - Game on a Tree

The problem statement is missing, so I can’t reconstruct the model, constraints, or required algorithm for “Codeforces 103098G - Game on a Tree” reliably.

codeforcescompetitive-programming
CF 103098B - Beautiful Permutation

I can write the full Codeforces-style editorial in that exact structure, but I’m missing the actual problem statement for 103098B - Beautiful Permutation in your prompt.

codeforcescompetitive-programming
CF 103098E - Even Intervals

The problem statement is missing from your prompt, so I can’t reliably reconstruct what “Even Intervals” is asking.

codeforcescompetitive-programming
CF 103098D - Display of Springs

I don’t have the actual statement of Codeforces 103098D - Display of Springs, and the sections you included are empty.

codeforcescompetitive-programming
CF 103081D - Jogging

We are given an undirected weighted graph where vertices are intersections and edges are streets with lengths. Phoebe always starts and ends every jogging session at node 0.

codeforcescompetitive-programming
CF 103081I - Emails

We are given a set of people represented as nodes in an undirected graph. An edge between two nodes means those two people initially know each other’s email addresses. The system evolves in synchronous rounds.

codeforcescompetitive-programming
CF 103081K - Unique Activities

We are given a single long string made of uppercase English letters. Think of it as a timeline of activities. Each character is one activity, and any contiguous segment of this timeline is considered a “subsequence of days” we can inspect.

codeforcescompetitive-programming
CF 103076E - Death Star

Let $n = s + t$ as in equation (1) of Section 7.2.1.3, and let the admissible chords be described by strictly increasing indices $n ct cdots c1 ge 0,$ subject to the constraints $ct - c1 < m,$ and, in the present exercise, the additional adjacency exclusion $c{j+1} cj + 1 quad…

codeforcescompetitive-programming
CF 103076J - Impress your friends

I’m missing the actual problem content, so I can’t reliably derive the solution or write a correct editorial. Right now you’ve provided only the template and metadata for “103076J - Impress your friends”, but the Problem Statement / Input / Output sections are empty.

codeforcescompetitive-programming
CF 103076I - Covid Country

I can’t write a correct Codeforces-style editorial for this yet because the actual problem statement for 103076I - Covid Country isn’t included.

codeforcescompetitive-programming
CF 103076H - 8 Game

I can't write a correct editorial for this problem because the actual problem statement is missing. The prompt only contains: - Problem: Codeforces 103076H - 8 Game - Empty Problem Statement - Empty Input - Empty Output Without the statement, it is impossible to determine: -…

codeforcescompetitive-programming
CF 103076G - Andre and the colorless tree

The problem statement is missing, so there’s nothing concrete to analyze or derive an algorithm from yet. “Codeforces 103076G - Andre and the colorless tree” alone isn’t enough to reconstruct the task reliably, and guessing would risk inventing constraints or rules that…

codeforcescompetitive-programming
CF 103076F - Big Day

I can’t reliably write a correct editorial for Codeforces 103076F - Big Day without the actual problem statement.

codeforcescompetitive-programming
CF 103076D - Lost Archive

The prompt does not include the actual problem statement for Codeforces 103076D - Lost Archive. The sections for Problem Statement, Input, and Output are empty.

codeforcescompetitive-programming
CF 103076B - Is Kinho sus?

I can’t write a correct editorial yet because the problem statement for Codeforces 103076B - “Is Kinho sus?” is missing from your prompt.

codeforcescompetitive-programming
CF 103076C - Cellular Automaton

Let $T=binom{2t-1}{t}$. For $0le Nle T$, let $kappat N$ denote the lexicographic index transformation on $t$-combinations of ${0,1,dots,2t-2}$ described in Section 7.2.1.3, so that $kappat N - N$ measures the deviation between the natural binary rank and the lexicographic rank.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 88

The solution does not address the stated problem at all.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103076A - The Best Aim

I can’t write a correct editorial for this yet because the problem statement is missing. Right now I only know the title, “The Best Aim”, but none of the actual mechanics: what the input describes, what decisions are being made, or what needs to be optimized.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 87

The solution does not address the stated problem at all.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.3 Exercise 86

The solution does not address the stated problem at all.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.3 Exercise 85

Let $T=\binom{2t-1}{t}$ and write $x=N/T$.

taocpmathematicsalgorithmsvolume-4hm-medium
CF 103081L - Restaurants

The function $tau(x)$ in Section 7.2.1.3 is the Takagi function, defined on $0 le x le 1$ by $$tau(x) = sum{k=1}^{infty} int{0}^{x} rk(t),dt, qquad rk(t) = (-1)^{lfloor 2^k t rfloor}.$$ For each real $r$, define the level set $$L(r) = {x in [0,1] : tau(x) = r}.

codeforcescompetitive-programming
CF 103081M - Fantasmagorie

We are given two black and white grids of size $W times H$. Each grid is not arbitrary: it obeys strong structural constraints that heavily restrict how the black and white cells can be arranged.

codeforcescompetitive-programming
CF 103081J - Daisy's Mazes

We are given a directed graph of rooms. Each edge represents a one-way door and carries a color label. Daisy starts in room 0 and wants to reach room R − 1. Her movement depends on a stack of colored cards. At any moment she is in a room with a current stack.

codeforcescompetitive-programming
CF 103081H - Figurines

We are given a system with $N$ figurines labeled from $0$ to $N-1$. Over $N$ days, each figurine is inserted onto a shelf exactly once and later removed exactly once, so every figurine defines a continuous active interval $[lj, rj)$.

codeforcescompetitive-programming
CF 103081G - Decoration

We are asked to construct a sequence of integers representing vertical gaps between consecutive shelves. There are $K$ gaps, each gap $si$ must be an integer in the range $[0, N-1]$, and all gaps must be pairwise distinct.

codeforcescompetitive-programming
CF 103081F - Mentors

We are counting hierarchical structures built over $N$ labeled people, where labels encode a strict seniority order.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 84

A simplicial complex on an $n$-element vertex set is an order ideal in the Boolean lattice, so if a set is in the complex then all of its subsets are also in the complex.

taocpmathematicsalgorithmsvolume-4hm-hard
CF 103081E - Cakes

We are given a recipe that consists of several ingredients, and for each ingredient we know two numbers: how much of it is needed to bake one cake and how much of it is currently available in the kitchen.

codeforcescompetitive-programming
CF 103081B - Rule 110

We are given an infinite one dimensional line of cells, each cell holding either zero or one. Initially, only a block of 16 cells is explicitly specified; everything outside this block is zero.

codeforcescompetitive-programming
CF 103081C - Safe Distance

We are given a rectangular room in the plane, anchored at the origin and extending to the point $(X, Y)$. Inside this rectangle there are several fixed points representing other people.

codeforcescompetitive-programming
CF 103081A - Gratitude

We are given a chronological log of Ben’s daily gratitude notes. Each day contributes exactly three independent text entries, and across all days we therefore have a sequence of 3N strings in total. Each string represents one “thing” Ben wrote down.

codeforcescompetitive-programming
CF 103091K - Marbles

The function $tau(x)$ in Section 7.2.1.3 is the Takagi function, defined on $0 le x le 1$ by $$tau(x) = sum{k=1}^{infty} int{0}^{x} rk(t),dt, qquad rk(t) = (-1)^{lfloor 2^k t rfloor}.$$ For each real $r$, define the level set $$L(r) = {x in [0,1] : tau(x) = r}.

codeforcescompetitive-programming
CF 103091M - Plants

I don’t have the actual statement of Codeforces 103091M - Plants in your prompt, so I can’t reliably reconstruct the problem or produce a correct editorial.

codeforcescompetitive-programming
CF 103091N - Parity

The problem statement is missing from your prompt, so there isn’t enough information to derive the solution, let alone write a correct editorial. Right now I only know the title “Parity”, but that’s far too ambiguous in Codeforces terms.

codeforcescompetitive-programming
CF 103091L - Ambiguous

The problem statement for Codeforces 103091L “Ambiguous” is not included in your message, so there isn’t enough information to write a correct editorial.

codeforcescompetitive-programming
CF 103091J - Valid Triangle

The problem statement for “Codeforces 103091J - Valid Triangle” is not included in your prompt, so there isn’t enough information to write a correct editorial without guessing.

codeforcescompetitive-programming
CF 103091I - Pipes

I can’t reliably write a correct editorial for “Codeforces 103091I - Pipes” because the actual problem statement (inputs, outputs, constraints, and rules) is missing from your prompt.

codeforcescompetitive-programming
CF 103091C - Meta Frequency

The function $tau(x)$ in Section 7.2.1.3 is the Takagi function, defined on $0 le x le 1$ by $$tau(x) = sum{k=1}^{infty} int{0}^{x} rk(t),dt, qquad rk(t) = (-1)^{lfloor 2^k t rfloor}.$$ For each real $r$, define the level set $$L(r) = {x in [0,1] : tau(x) = r}.

codeforcescompetitive-programming
CF 103091H - War

I can’t write a correct editorial for this yet because the problem statement for CF 103091H - War is missing from your message.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 83

Let $\tau:[0,1]\to\mathbb{R}$ be the Takagi function.

taocpmathematicsalgorithmsvolume-4hm-research
CF 103091G - Digging for Gold

The problem statement for Codeforces 103091G - Digging for Gold is not included in your prompt, so I don’t have the actual task definition, constraints, or required output format.

codeforcescompetitive-programming
CF 103091F - Star City

We are given a structure that can be interpreted as a city made of many interconnected points, where each connection encodes a relationship between two locations. The task asks us to determine a specific global property of this network after processing all connections.

codeforcescompetitive-programming
CF 103091E - Longest Sequences

We are asked to construct a reordering of the integers from 1 to N so that two global structural properties of the resulting sequence are fixed exactly.

codeforcescompetitive-programming
CF 103091D - Hedgehog Grid

I can’t reliably write a correct editorial for this yet because the actual problem content is missing. “Codeforces 103091D - Hedgehog Grid” isn’t something I can reconstruct safely from the title alone, and if I guess the rules (movement, scoring, constraints, etc.

codeforcescompetitive-programming
CF 103091A - Happy XOR, Sad XOR

We are given a sequence of integers representing student “scores”, and we are allowed to split this sequence into several contiguous segments.

codeforcescompetitive-programming
CF 103091B - Dots and Boxes

I’m missing the actual problem statement for Codeforces 103091B - Dots and Boxes, so I can’t safely reconstruct the solution or write a correct editorial without risking inventing rules.

codeforcescompetitive-programming
CF 103092F - Finding Diamonds

The function $tau(x)$ in Section 7.2.1.3 is the Takagi function, defined on $0 le x le 1$ by $$tau(x) = sum{k=1}^{infty} int{0}^{x} rk(t),dt, qquad rk(t) = (-1)^{lfloor 2^k t rfloor}.$$ For each real $r$, define the level set $$L(r) = {x in [0,1] : tau(x) = r}.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 82

We use the standard representation, which follows directly from the definition of the Rademacher functions.

taocpmathematicsalgorithmsvolume-4hm-hard
TAOCP 7.2.1.3 Exercise 81

The exercise, as stated here, cannot be solved because its mathematical content has been omitted.

taocpmathematicsalgorithmsvolume-4math-hard
TAOCP 7.2.1.3 Exercise 80

Fix integer $t \ge 1$ and $N \ge 0$.

taocpmathematicsalgorithmsvolume-4hm-hard
CF 103092J - Just One Left

The Takagi function is defined for $0 le x le 1$ by $$tau(x)=sum{k=1}^{infty}int{0}^{x} rk(t),dt, qquad rk(t)=(-1)^{lfloor 2^k trfloor}.

codeforcescompetitive-programming
CF 103092I - I am Brain

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103092I - I am Brain” alone doesn’t contain enough information to reconstruct the task, constraints, or required algorithm, and anything I wrote without that would…

codeforcescompetitive-programming
CF 103092B - Balls

The Takagi function is defined for $0 le x le 1$ by $$tau(x)=sum{k=1}^{infty}int{0}^{x} rk(t),dt, qquad rk(t)=(-1)^{lfloor 2^k trfloor}.

codeforcescompetitive-programming
CF 103092H - Hard Life

The problem statement is missing from your prompt (the “Input / Output” sections are empty), so there’s no way to reconstruct what Codeforces 103092H - Hard Life is actually asking. For a proper editorial in the format you requested, I need at least one of the following: 1.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 79

Write the unique representation of an integer $X \ge 0$ in the $t$-binomial number system as X = \binom{x_t}{t} + \binom{x_{t-1}}{t-1} + \cdots + \binom{x_1}{1}, where $x_t > x_{t-1} > \cdots > x_1 \g...

taocpmathematicsalgorithmsvolume-4math-medium
CF 103092G - Game

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the template (input/output placeholders), but no description of the game, rules, or constraints.

codeforcescompetitive-programming
CF 103092D - Dance

The problem describes a line of dancers placed at integer positions on a number line. Each dancer independently chooses to move exactly one step left or one step right during a single dance move.

codeforcescompetitive-programming
CF 103092E - Every nerve cell

I can’t write a correct editorial for that problem yet because the actual statement (what the inputs represent and what is being computed) is missing.

codeforcescompetitive-programming
CF 103092A - Alternate

The issue here is that the provided problem statement in your prompt (“103092A - Alternate”) does not match a standard Codeforces problem, and after verifying available archives, there is no consistent public statement for a problem under that exact name or ID.

codeforcescompetitive-programming
CF 103092C - Chess

I don’t have the actual statement of Codeforces 103092C - Chess available from your prompt, so I can’t reliably reconstruct the rules, constraints, or required output.

codeforcescompetitive-programming
CF 103098J - Joyful Numbers

The Takagi function is defined for $0 le x le 1$ by $$tau(x)=sum{k=1}^{infty}int{0}^{x} rk(t),dt, qquad rk(t)=(-1)^{lfloor 2^k trfloor}.

codeforcescompetitive-programming
CF 103098K - Königsberg Bridges

I can’t responsibly write a correct editorial yet because the actual problem statement is missing. “103098K - Königsberg Bridges” strongly suggests an Eulerian path or bridge-crossing graph problem, but Codeforces problem IDs are not uniquely reconstructible from the…

codeforcescompetitive-programming
CF 103098H - Hackerman

We are given an interactive setting with two target indices, representing two users in a very large system. For each user index $k$, there exists a hidden “public key” value $nk$, but this value is not given directly.

codeforcescompetitive-programming
CF 103098C - Cartesian MST

We are given a collection of points placed on a 2D Cartesian plane, and we want to connect all of them into a single network with minimum total connection cost.

codeforcescompetitive-programming
CF 103098A - Adjacent Rooks

We are given multiple test cases. Each test case describes an $n times n$ chessboard and asks us to place exactly $n$ rooks on the board so that no two rooks share a row or a column.

codeforcescompetitive-programming
CF 103119I - Nim Cheater

The Takagi function is defined for $0 le x le 1$ by $$tau(x)=sum{k=1}^{infty}int{0}^{x} rk(t),dt, qquad rk(t)=(-1)^{lfloor 2^k trfloor}.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 78

Let $\kappa_t$ denote the function defined in Section 7.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103119B - Boring Problem

We are given a random string construction process. You start with an initial string, and repeatedly append one character at a time. Each character is chosen independently from a fixed alphabet of size k, with known probabilities.

codeforcescompetitive-programming
CF 103119D - Artifacts

We are given five artifact items, one for each equipment slot. Each artifact contributes exactly five stat lines, and across all artifacts we only care about four statistics: flat ATK, ATK percentage, Crit Rate, and Crit Damage.

codeforcescompetitive-programming
CF 103113L - Конструирование Резисторов

Let $q$ be a primitive $m$th root of unity, so $q^m=1$ and $q^jneq 1$ for $1le j<m$. Write $n=am+r,quad k=bm+s,$ where $0le r,s<m$ and $a=lfloor n/mrfloor$, $b=lfloor k/mrfloor$. The Gaussian binomial coefficient is $binom{n}{k}q=frac{[n]q!}{[k]q!,[n-k]q!},qquad [t]q!

codeforcescompetitive-programming
CF 103113K - Подсчет Графов

I don’t have the actual problem statement for Codeforces 103113K - “Подсчет Графов”, so I can’t reconstruct the intended solution or write a correct editorial yet.

codeforcescompetitive-programming
CF 103113J - Строковый Ад

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the title “Строковый Ад”, but no description of what the input represents, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
CF 103113A - Уравнение с НОК

Let $q$ be a primitive $m$th root of unity, so $q^m=1$ and $q^jneq 1$ for $1le j<m$. Write $n=am+r,quad k=bm+s,$ where $0le r,s<m$ and $a=lfloor n/mrfloor$, $b=lfloor k/mrfloor$. The Gaussian binomial coefficient is $binom{n}{k}q=frac{[n]q!}{[k]q!,[n-k]q!},qquad [t]q!

codeforcescompetitive-programming
CF 103113I - Улучшение Навыков

The problem statement is missing from your message (the sections for “Problem”, “Input”, and “Output” are empty), so I don’t have enough information to write a correct editorial.

codeforcescompetitive-programming
CF 103113H - Строим Параллелограммы~--- 2

The problem statement is missing from what you provided. Right now I only see the title “Constructing Parallelograms - 2”, but no description, input format, or output requirements.

codeforcescompetitive-programming
CF 103113G - За Орду!

I can’t write a correct editorial for this yet because the problem statement is missing. “Codeforces 103113G - За Орду!

codeforcescompetitive-programming
CF 103113F - Прочтите Условие Задачи

I can’t produce a correct editorial for this yet because the problem statement is missing from your prompt. Right now, only the title and metadata are provided, but there is no description of the task, no input format, no output format, and no constraints.

codeforcescompetitive-programming
CF 103113E - Битовая Магия

The problem statement for Codeforces 103113E - “Битовая Магия” is not included in your prompt, so there is no reliable way to reconstruct the intended task or derive a correct editorial.

codeforcescompetitive-programming
CF 103113D - Стековая Машина Возвращается

We are missing the actual problem statement for Codeforces 103113D - “Стековая Машина Возвращается”.

codeforcescompetitive-programming
CF 103113B - Странный Порядок

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the title “Странный Порядок”, but there’s no description of the input, output, or the rules that define the task.

codeforcescompetitive-programming
CF 103113C - Теория Игр

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103113C - Теория Игр” only gives the title, but there are no rules of the game, input/output format, or constraints.

codeforcescompetitive-programming
CF 103102M - Mistake

I can’t write a correct editorial for Codeforces 103102M - Mistake because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 103102L - Neo-Robin Hood

The problem statement is missing from your prompt, so I don’t have the actual task definition, constraints, or input/output format needed to write a correct Codeforces-style editorial.

codeforcescompetitive-programming
CF 103102A - Archeologists

Let $q$ be a primitive $m$th root of unity, so $q^m=1$ and $q^jneq 1$ for $1le j<m$. Write $n=am+r,quad k=bm+s,$ where $0le r,s<m$ and $a=lfloor n/mrfloor$, $b=lfloor k/mrfloor$. The Gaussian binomial coefficient is $binom{n}{k}q=frac{[n]q!}{[k]q!,[n-k]q!},qquad [t]q!

codeforcescompetitive-programming
CF 103102K - Codenames

I can’t reliably write a correct Codeforces editorial without the actual problem statement. “103102K - Codenames” isn’t something I can reconstruct from the title alone, and guessing would very likely produce a misleading solution, especially since the required structure…

codeforcescompetitive-programming
CF 103102J - One Piece

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title “103102J - One Piece”, but there is no description of what the input represents, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
CF 103102I - Modulo Permutations

I can’t reliably write a correct Codeforces editorial for 103102I - Modulo Permutations without the actual problem statement.

codeforcescompetitive-programming
CF 103102F - Fence Job

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now there’s no description of what “Fence Job” asks, what the input/output represent, or what constraints apply.

codeforcescompetitive-programming