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tamnd's digital brain — notes, problems, research

43815 notes

CF 103059A - Alaska Don't Release Them

The problem statement is missing, so there isn’t enough information to reconstruct the task, constraints, or intended solution. To write a correct Codeforces-style editorial, I need at least: the full statement (or a screenshot/text), plus any samples if available.

codeforcescompetitive-programming
CF 103059C - Chess Tournament

I can write the full editorial, but I’m missing the actual problem statement for Codeforces 103059C - Chess Tournament.

codeforcescompetitive-programming
CF 103061L - et the wind tell you

Let $ct cdots c1$ denote the lexicographic representation of an $(s,t)$-combination in decreasing order as in (3), and let $bs cdots b1$ denote the dual representation given by the positions of the zeros as in (5).

codeforcescompetitive-programming
CF 103061N - anikore

I can’t write a correct editorial for this yet because the actual problem statement for “Codeforces 103061N - anikore” isn’t included in your message.

codeforcescompetitive-programming
CF 103061M - abushii Omoi

The problem statement is missing from your prompt, so there isn’t enough information to derive the solution or write a correct Codeforces-style editorial. Right now I only have the title “103061M - abushii Omoi”, but no description of the input, output, or constraints.

codeforcescompetitive-programming
CF 103061K - ätzlein Cocktail

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103061K - ätzlein Cocktail” isn’t enough to reconstruct the task reliably, and guessing would almost certainly produce a wrong solution and misleading reasoning.

codeforcescompetitive-programming
CF 103061I - cy Resurrection

The problem statement for Codeforces 103061I - cy Resurrection is missing in your prompt, so I don’t have enough information to derive the solution, constraints, or examples.

codeforcescompetitive-programming
CF 103061B - lazing Riff

Let $ct cdots c1$ denote the lexicographic representation of an $(s,t)$-combination in decreasing order as in (3), and let $bs cdots b1$ denote the dual representation given by the positions of the zeros as in (5).

codeforcescompetitive-programming
CF 103061J - uvenile Galant

I can’t write a correct Codeforces editorial from just the title “103061J - uvenile Galant” because the actual problem statement, constraints, and task definition are missing.

codeforcescompetitive-programming
CF 103061H - armless Sweetie

I don’t have the actual statement for Codeforces 103061H - armless Sweetie, and without it I can’t reliably reconstruct the intended model, constraints, or solution approach.

codeforcescompetitive-programming
CF 103061G - liding Champion

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 103061G - “liding Champion” is missing from your prompt.

codeforcescompetitive-programming
CF 103061F - leeing Sunlight

The problem statement is missing from the prompt, so I can’t write a correct editorial yet. Codeforces solutions are completely driven by the exact rules of the task, and without knowing what “103061F - leeing Sunlight” actually asks (inputs, outputs, constraints, and…

codeforcescompetitive-programming
CF 103061D - andelion Knight

You’re right to flag this immediately. I cannot produce a correct editorial yet because the actual problem statement for Codeforces 103061D - “andelion Knight” is not available in the prompt, and it does not correspond cleanly to any publicly accessible CF problem under…

codeforcescompetitive-programming
CF 103061E - clipsing Star

I can’t write a correct Codeforces-style editorial for “103061E - clipsing Star” without the actual problem statement.

codeforcescompetitive-programming
CF 103061C - hivalric Blossom

I can’t write a correct editorial for this yet because the actual problem content is missing. Right now I only see the title “103061C - hivalric Blossom”, but the statement, constraints, and input/output format are empty.

codeforcescompetitive-programming
CF 103061A - stral Reflection

We are missing the actual statement of Codeforces 103061A - stral Reflection in your prompt, so there is no reliable way to reconstruct the problem model, constraints, or solution.

codeforcescompetitive-programming
CF 103064G - Ulearn

We are given a repeated workflow that transforms each programming task from start to finish. Every task goes through four stages in order.

codeforcescompetitive-programming
CF 103064F - Трудный выбор

We are given a collection of candidate groups of friends, where each group has a known size. Separately, we are given several “counting-out” procedures, where each procedure is defined by a number of steps, and the selection is done on a circle of people.

codeforcescompetitive-programming
CF 103064C - Baba is You

Let $(a{ij})$ be an $mtimes n$ contingency table with fixed row sums $sum{j=1}^n a{ij}=ri quad (1le ile m)$ and column sums $sum{i=1}^m a{ij}=cj quad (1le jle n),$ where $sumi ri=sumj cj$.

codeforcescompetitive-programming
CF 103064D - Он вам не ферзь

We are given a square grid of size $M times M$, with up to $N$ white kings placed on distinct cells. For each test case, we must count how many empty cells can host a black queen such that two conditions hold simultaneously.

codeforcescompetitive-programming
CF 103064E - Сила есть, ум тоже нужен

Each employee in the company is a node in a rooted tree. Employee 1 is the root, and every other employee has exactly one direct manager, forming a hierarchy where edges point from a manager to their direct subordinates.

codeforcescompetitive-programming
CF 103064B - Как пройти в столовую

We are given a rectangular grid that represents a building corridor system. Each cell of the grid is either empty, a wall, a key, a locked door, or the starting position. From the starting cell, a person moves according to a fixed sequence of directions.

codeforcescompetitive-programming
CF 103064A - Снова ИИ

We are working with a function built from integer floor division, applied twice. For a fixed number $N$, every candidate value $X$ in the range $[1, N]$ is tested by first computing $lfloor N / X rfloor$, and then applying the same operation again using that result as a divisor.

codeforcescompetitive-programming
CF 103069I - Plants vs Zombies

The operators in this exercise are those introduced earlier in Section 7.2.1.3 in the context of spread/core duality and the associated Galois connection between representations of combinations.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 92

Let $a_1 \ge a_2 \ge \cdots \ge a_m \ge 1$ be a partition of $n$ into $m$ parts that is optimally balanced, meaning $|a_i-a_j|\le 1$ for all $1\le i,j\le m$.

taocpmathematicsalgorithmsvolume-4math-hard
CF 103069M - Fillomino

We are given a toroidal grid of size (n times m), meaning the grid wraps around both horizontally and vertically. Each cell touches its four neighbors, and the top edge connects to the bottom edge while the left edge connects to the right edge.

codeforcescompetitive-programming
CF 103069L - Square

We are given a sequence of integers and we are allowed to assign a strictly positive multiplier to every position.

codeforcescompetitive-programming
CF 103069K - Allin

We are given a simplified heads-up Texas hold ’em situation with only two players and no folding. Each test case provides five cards: two private cards for Wolf Chicken and three shared community cards representing the flop.

codeforcescompetitive-programming
CF 103069J - Circle

We are given a convex polygon described by its vertices in counterclockwise order. Think of this polygon as a rigid shape in the plane. We also fix a radius $r$. Now we imagine placing a circle of radius $r$ anywhere in the plane by choosing its center $p$.

codeforcescompetitive-programming
CF 103069H - Prof. Pang Earning Aus

We are given a system with three interchangeable resources: Aus, balloons, and candies. At the start, Prof. Pang has exactly one Au and zero of the other two. There are two stores that allow conversions between these resources using fixed exchange rules.

codeforcescompetitive-programming
CF 103069G - Prof. Pang's sequence

We are given a fixed array and many queries over contiguous segments of it. For each query interval $[l, r]$, we must count how many subarrays $[i, j]$ fully contained inside that interval have the property that the number of distinct values inside the subarray is odd.

codeforcescompetitive-programming
CF 103069B - Rectangle Flip 2

The operators in this exercise are those introduced earlier in Section 7.2.1.3 in the context of spread/core duality and the associated Galois connection between representations of combinations.

codeforcescompetitive-programming
CF 103069F - Rooks

We are given two sets of points on an infinite integer grid. One set belongs to Prof. Pang and the other belongs to Prof. Shou.

codeforcescompetitive-programming
CF 103069E - Tube Master III

We are given a rectangular grid of crossings connected by horizontal and vertical tubes. At every crossing, we are allowed to either not use any tube or use exactly two tubes incident to that crossing.

codeforcescompetitive-programming
CF 103069D - City Brain

We are given an undirected graph where every road initially takes one second to traverse. We are allowed to invest money into individual roads, and each dollar increases the “speed level” of that road by one. If a road has speed level $a$, traversing it takes $1/a$ seconds.

codeforcescompetitive-programming
CF 103069C - Random Shuffle

We are given the final outcome of a deterministic shuffling process applied to the sequence of integers from 1 to n. The process builds the array incrementally.

codeforcescompetitive-programming
CF 103069A - Namomo Subsequence

We are given a single long string consisting of letters and digits. From this string we want to count how many ways we can choose six positions in increasing order such that the chosen characters “match the pattern structure” of the word namomo.

codeforcescompetitive-programming
CF 103074B - Игры с кольцами

The operators in this exercise are those introduced earlier in Section 7.2.1.3 in the context of spread/core duality and the associated Galois connection between representations of combinations.

codeforcescompetitive-programming
CF 103074H - Теннис

The problem statement for Codeforces 103074H - “Теннис” is not included in your message, so there is no way to correctly reconstruct the task, constraints, or required algorithm.

codeforcescompetitive-programming
CF 103074G - Водный пазл

I can’t write a correct editorial without the actual problem statement. “Codeforces 103074G - Водный пазл” is not included in your prompt, so I don’t know what the input describes, what the task is, or what needs to be computed.

codeforcescompetitive-programming
CF 103074F - Зов Древних

The problem statement is missing from the prompt, so I don’t have enough information to reconstruct what “Codeforces 103074F - Зов Древних” is asking.

codeforcescompetitive-programming
CF 103074E - День рождения

I’m missing the actual problem statement for Codeforces 103074E - День рождения in your message, so I can’t reliably derive the solution or write a correct editorial.

codeforcescompetitive-programming
CF 103074D - Рукопожатия

The problem statement is missing from your prompt, so I don’t actually have enough information to reconstruct what “103074D - Рукопожатия” is asking.

codeforcescompetitive-programming
CF 103074A - Numbers (Div-2 only!)

The problem statement is missing from your prompt, so there is nothing concrete to restate, analyze constraints for, or derive an algorithm from. Right now we only have the template and metadata, but no description of what “Numbers (Div-2 only!

codeforcescompetitive-programming
CF 103074C - Synonymous Words Number System

I can’t write a correct Codeforces editorial for this problem yet because the statement is missing. “Synonymous Words Number System” could refer to several different tasks (string equivalence classes, DSU on synonyms, hashing word mappings, etc.

codeforcescompetitive-programming
TAOCP 7.2.1.3 Exercise 91

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
CF 103075J - Рудольф и марсоход

The task describes a rover that moves along a one-dimensional route of stations from position 1 to position N. Between every pair of consecutive stations there is a road segment. For each segment, the rover has two ways to traverse it.

codeforcescompetitive-programming
CF 103075A - Рудольф и масштабирование

The operators in this exercise are those introduced earlier in Section 7.2.1.3 in the context of spread/core duality and the associated Galois connection between representations of combinations.

codeforcescompetitive-programming
CF 103075I - Рудольф и M&M's

I don’t have the actual statement of Codeforces 103075I (“Рудольф и M&M's”) in your prompt, so I can’t write a correct editorial yet without risking inventing details.

codeforcescompetitive-programming
CF 103075H - Рудольф и гидродинамика

I can’t write a correct editorial for this problem yet because the actual problem statement is missing. Right now I only have the title “Рудольф и гидродинамика”, but no description of the process, inputs, outputs, or constraints.

codeforcescompetitive-programming
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