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tamnd's digital brain — notes, problems, research

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CF 104848J - Spectacular Ending

We are given a system of states, where each state behaves like a custom dice roll. From a current state, the game “rolls a dice” whose faces are not just uniform outcomes, but a collection of weighted faces with known probabilities.

codeforcescompetitive-programming
CF 104848K - Efficient Interception

The problem statement in your prompt is incomplete and corrupted. The sample input and sample output are truncated, and crucial parts of the statement are missing or malformed.

codeforcescompetitive-programming
CF 104848I - 1\%-Euclidean

We are given a set of points on a 2D plane, and we are asked to compute the sum of Euclidean distances over all unordered pairs of points. For every pair of distinct points, we take the straight-line distance between them and add it to a global total.

codeforcescompetitive-programming
CF 104848H - Roman Palindromes

I don't have enough information to write a correct editorial and solution for this problem. The statement you provided contains the problem description, but it is missing the most important part needed to derive the algorithm: the official definition of what counts as a…

codeforcescompetitive-programming
CF 104848F - Build the Non-Cactus

We are asked to construct a connected simple undirected graph on vertices numbered from 1 to n. The graph must not be a cactus, meaning it must contain at least two simple cycles that overlap in at least two vertices. Self-loops and multiple edges are forbidden.

codeforcescompetitive-programming
CF 104848E - Construct The Integer

We are given a positive integer $x$. From this number we conceptually generate a family of numbers by permuting its decimal digits in every possible way, then removing any leading zeros that might appear after permutation.

codeforcescompetitive-programming
CF 104848G - Double Elimination

The requested editorial cannot be written correctly because the prompt is missing essential information. The problem statement describes the tournament format, but it does not describe how to reconstruct a team's finishing position from its win/loss string.

codeforcescompetitive-programming
CF 104848D - Christmas Children Circle

I don't have enough information to write a correct editorial and solution because the problem statement in your prompt is corrupted.

codeforcescompetitive-programming
CF 104848B - Gleb and Liteyny Avenue

We are given a straight road segment from position 0 to position L. Gleb walks from 0 toward L at speed 1 meter per second, and at certain integer positions there are pedestrian crossings where he may cross to the other side of the avenue.

codeforcescompetitive-programming
CF 104848C - Socks Drying

We are simulating a randomized “sock pairing” process after a wash. All socks are grouped by color, and within each color the socks are indistinguishable. The process repeatedly removes a random sock from the machine.

codeforcescompetitive-programming
CF 104848A - A Non-Palindromic Modification

We are given an integer array. We must increase exactly one element by 1 and then check whether the resulting array is not a palindrome. The task is to decide whether such a choice of position exists. An array is palindromic when every element matches its mirrored counterpart.

codeforcescompetitive-programming
CF 104849K - New Year Festival

I can’t write a correct Codeforces editorial for this problem yet because the actual problem statement is missing from your prompt. Right now I only see the title “New Year Festival”, but no description of: what the inputs are, what needs to be computed, or any constraints.

codeforcescompetitive-programming
CF 104849H - Cake Decoration

We are given a convex polygon representing the outline of a cake. Each vertex is connected by straight edges, forming a closed shape. The decoration process repeatedly “trims” the cake in a very structured way.

codeforcescompetitive-programming
CF 104849J - Traveling Salesperson in an Island

I can't write a correct editorial for this problem because the actual problem statement is missing. For Codeforces 104849J - Traveling Salesperson in an Island, the statement you've provided only contains: "Please read the problem statements here.

codeforcescompetitive-programming
CF 104849I - Quiz Contest

I can’t produce a correct Codeforces editorial from this prompt because the actual problem content is missing. The link placeholder “Please read the problem statements here” doesn’t include the statement, so there is no way to reconstruct what “Quiz Contest” is…

codeforcescompetitive-programming
CF 104849G - Remodeling the Dungeon

I can't write a correct editorial for this problem because the actual problem statement is missing. The prompt only contains: Problem: Codeforces 104849G - Remodeling the Dungeon followed by "Please read the problem statements here.

codeforcescompetitive-programming
CF 104849F - Make a Loop

I can’t reliably reconstruct Codeforces 104849F - Make a Loop from the provided prompt alone because the actual statement link content is missing and Codeforces Gym problems are not uniquely identifiable from the ID without the original page text.

codeforcescompetitive-programming
CF 104849E - Incredibly Cute Penguin Chicks

I can’t reliably write an editorial for this yet because the actual problem statement for “Codeforces 104849E - Incredibly Cute Penguin Chicks” isn’t included in your message, and I don’t have access to fetch it from Codeforces directly.

codeforcescompetitive-programming
CF 104849D - Move One Coin

The problem statement in your prompt is incomplete. It only contains: Problem: Codeforces 104849D - Move One Coin Problem Statement: Please read the problem statements here. The actual statement, input format, output format, and constraints are missing.

codeforcescompetitive-programming
CF 104849C - Secure the Top Secret

I can’t reliably reconstruct Codeforces 104849C “Secure the Top Secret” from the sources available, and I don’t want to hallucinate an editorial for a problem whose constraints and exact rules are unclear.

codeforcescompetitive-programming
CF 104849B - Interactive Number Guessing

I can’t reliably write a correct Codeforces editorial from what you’ve provided, because the actual problem statement is missing (“Please read the problem statements here” with no content).

codeforcescompetitive-programming
CF 104849A - Hasty Santa Claus

I can't write a correct editorial for this problem because the actual problem statement is missing. The prompt only contains: "Please read the problem statements here." without the linked statement, input format, output format, or samples.

codeforcescompetitive-programming
CF 1048514 - Cakes

We are distributing a total number of cakes among a fixed number of children. Every child must receive exactly the same amount, but the cook is allowed to cut cakes into halves, meaning each cake can contribute either a whole unit or two half-units.

codeforcescompetitive-programming
CF 1048515 - Business Trips to Courses

We are given a sequence of scheduled trips, each describing an interval of days during which Vasily must be present in a specific city. Every trip is active on all days from its start day to its end day, inclusive.

codeforcescompetitive-programming
CF 1048512 - Robot Program

We are given an 8 by 8 grid with obstacles and one special cell, the finish located at the bottom-right corner. A robot can start from any empty cell in the grid. We must output a program consisting of movement commands.

codeforcescompetitive-programming
CF 1048513 - Number of Words

We are asked to count how many valid strings can be formed using only three characters: a, o, and c, with two constraints. Each string must have fixed length N, and no character is allowed to appear more than K times inside a single string.

codeforcescompetitive-programming
CF 1048511 - Rhombuses

We are working with an infinite grid where every cell contains a natural number, arranged in expanding rhombus-shaped layers around a central cell. The central cell contains the value 1.

codeforcescompetitive-programming
CF 1048521 - Rhombic Order

We are given a grid with a special numbering rule: the integer 1 sits at the origin, and numbers expand outward in layers shaped like diamonds.

codeforcescompetitive-programming
CF 1048523 - Business Trips

We are given a list of scheduled business trips for an employee. Each trip occupies a continuous interval of days and specifies a city.

codeforcescompetitive-programming
CF 1048535 - Очередная задача про кузнечика

We are given a sequence of pillars, each with a height. A frog starts on some pillar and wants to reach another pillar to the right, but it can only jump forward and each jump can skip at most k positions.

codeforcescompetitive-programming
CF 1048534 - Очередная задача про игру с камнями

We are given several piles of stones. Each pile has a fixed allowable range of how many stones we are allowed to take from it. From pile $i$, we must choose an integer $xi$ such that $li le xi le ri$.

codeforcescompetitive-programming
CF 1048532 - Очередная задача про хорошие строки

We are given a collection of strings, each consisting only of digits from 0 to 9. For any ordered pair of indices $(i, j)$ with $i < j$, we concatenate the two strings $si$ and $sj$.

codeforcescompetitive-programming
CF 1048531 - Очередная задача про математику

We start with two very large integers, call them $a$ and $b$. We are allowed to perform at most $k$ operations, where each operation independently increases either $a$ by one or $b$ by one.

codeforcescompetitive-programming
CF 1048533 - Очередная задача про победу над монстрами

We are given a game world consisting of several dungeons, each containing a monster with a fixed strength value. The player starts with an initial strength and is allowed to enter any dungeon in any order.

codeforcescompetitive-programming
CF 104854K - Kenough Time

We are given a 2D continuous world split into two movement regimes by the horizontal line $y = 0$. Points with $y ge 0$ are land where Ken moves at speed $v{run}$, and points with $y < 0$ are sea where he moves at speed $v{swim}$, with $v{run} ge v{swim}$.

codeforcescompetitive-programming
CF 104854J - Judging Gifts

We can think of the situation as a directed graph where each gift type is a node and each possible exchange is a directed edge with a positive cost representing effort.

codeforcescompetitive-programming
CF 104854I - Intelligent Cat Embedding

We are given a fixed embedding space of size $k$. Every sentence we construct is a sequence of words, and each word acts like a set of deterministic “write operations” on this embedding vector. We start from a zero vector of length $k$.

codeforcescompetitive-programming
CF 104854H - Homogeneous Mixings

We are given a multiset of colored particles, where each particle is represented by a lowercase letter. The input string is already sorted, so equal letters appear in contiguous blocks.

codeforcescompetitive-programming
CF 104854G - Guess Gauss

We are given a single integer $d$, and we are told that two people independently computed triangular sums of the form $1 + 2 + dots + n$ and $1 + 2 + dots + m$, where $m n$. The only information we still have is the difference between these two sums, which equals $d$.

codeforcescompetitive-programming
CF 104854F - Factorial Prime

We are given a single integer $x$. Our task is to find the largest number $y$ that does not exceed $x$, with two properties at the same time. First, $y$ must be a prime number.

codeforcescompetitive-programming
CF 104854E - Elimination Bracket

We are given a string made of three possible characters: opening brackets, closing brackets, and wildcard symbols. Each wildcard can later be replaced independently by either an opening or a closing bracket.

codeforcescompetitive-programming
CF 104854D - District 42

We are given a single integer $n$, and we conceptually write down all positive integers from 1 up to $n$ one after another with no separators, forming one long digit string. For example, if $n = 15$, the string is 123456789101112131415.

codeforcescompetitive-programming
CF 104854A - Arthur The Ant

We are given a very large rectangular grid, but only a small number of special cells called lily pads are initially active. Two of these pads are always at the start cell and the target cell.

codeforcescompetitive-programming
CF 104854C - Continued Fractions

We are given a large integer $p$. Each test case asks us to look at all factorizations $p = a cdot b$, where both $a$ and $b$ are positive integers.

codeforcescompetitive-programming
CF 104854B - Beautiful Contest

We maintain a dynamic multiset of problems. Each problem has a difficulty value and a beauty value, and operations either insert or delete a specific problem instance. After every update, we are asked to compute the maximum possible total beauty of a valid “contest”.

codeforcescompetitive-programming
CF 104855F - Regular Covering

We are given a set of points on the plane and a regular polygon with a fixed number of sides $m$. The polygon is always centered at the origin, but we are free to rotate it.

codeforcescompetitive-programming
CF 104855E - Perfect Permutation

We are given three arrays of equal length, and our task is to build a permutation of indices from 1 to n. For each position i, the value assigned to that position in the permutation determines which of three rewards we collect at i.

codeforcescompetitive-programming
CF 104855D - Colorful Paths

We are given a directed graph where each edge carries a label called a color. Starting from node 1, we can walk along directed edges as many times as we want, and we are allowed to revisit nodes and reuse edges.

codeforcescompetitive-programming
CF 104855B - Yugandhar's Letter for Diya

We are given a very large rectangular grid. One cell is initially blue, and we are allowed to choose exactly $k$ additional cells and paint them pink. After this setup, two spreading processes take place alternately.

codeforcescompetitive-programming
CF 104855A - GCD,LCM and AVG

We are interacting with a hidden integer $x$ between $1$ and $10^9$. Our only tool is to ask queries of the form “give me some integer $a$” and receive back a value computed from how $a$ relates to $x$.

codeforcescompetitive-programming
CF 104855C - Hungry Shark

We are given a circular arrangement of boxes, each containing some number of identical items. A person starts at the first box and repeatedly performs a fixed routine: if the current box still has items, she removes exactly one item and increases a running counter, then she…

codeforcescompetitive-programming
CF 1048565 - Вечер кёрлинга

I don’t have the actual statement of Codeforces 1048565 (“Вечер кёрлинга”) available from your prompt, and without it I can’t reliably reconstruct the rules, constraints, or required algorithm.

codeforcescompetitive-programming
CF 1048564 - Задачи на печать!

I can’t reliably write a correct Codeforces-style editorial for “1048564 - Задачи на печать!” because the actual problem statement (input/output definition and constraints) is missing from your prompt.

codeforcescompetitive-programming
CF 1048563 - Телефонный справочник

We are working with a simple phone directory that stores associations between a person’s name and their phone number. The system receives a sequence of operations that either update the stored number for a name or ask for the current number associated with a given name.

codeforcescompetitive-programming
CF 1048562 - Рамка для рисунка

I can’t reliably reconstruct Codeforces problem 1048562 “Рамка для рисунка” from the identifier alone, and the available references point to multiple unrelated gym tasks rather than a single clear statement.

codeforcescompetitive-programming
CF 1048561 - Ферзь

I can’t reliably write a correct editorial for “Codeforces 1048561 - Ферзь” from just the title, because multiple different problems use that name (it simply means “Queen” in chess), and the solution depends entirely on the exact task.

codeforcescompetitive-programming
CF 104857L - Information Spread

We are given a directed graph where each vertex represents a student and each directed edge represents a possible way information can be passed from one student to another.

codeforcescompetitive-programming
CF 104857K - Campus Partition

We are given a tree representing a campus, where each node is a building and each building has a positive importance value. We must split the tree into several groups by removing some edges.

codeforcescompetitive-programming
CF 104857J - Takeout Delivering

We are given a connected undirected graph where each edge has a positive weight representing congestion. A path from node 1 to node n is not evaluated in the usual way. Instead of summing all edge weights, only the two largest edge weights along the path matter.

codeforcescompetitive-programming
CF 104857I - Linguistics Puzzle

We are given a strange “language system” where there are $n$ symbols and they behave like digits in a base-$n$ number system, but the mapping from digits to symbols is unknown.

codeforcescompetitive-programming
CF 104857H - Computational Complexity

We are given two mutually recursive functions that grow with the input size, but instead of depending on slightly smaller integers in a linear way, each function depends on the other function evaluated at a significantly smaller argument, specifically a halved version of the…

codeforcescompetitive-programming
CF 104857G - Streak Manipulation

We are given a binary string that represents attendance across a sequence of classes. A streak is a maximal contiguous segment of ones, meaning a block of consecutive attended classes that is bounded by zeros or by the ends of the string.

codeforcescompetitive-programming
CF 104857D - Balanced Array

We are given an array that grows one element at a time, and after each new element we must decide whether the current prefix has a certain structural property.

codeforcescompetitive-programming
CF 104857F - Colorful Balloons

We are given a sequence of balloon colors, where each balloon has a color represented by a short lowercase string. The task is to determine whether there exists a color that appears strictly more than half of the total number of balloons. If such a color exists, we output it.

codeforcescompetitive-programming
CF 104857E - Matrix Distances

We are given an $n times m$ grid where each cell contains an integer color. For every color, we look at all cells having that color and consider every ordered pair of such cells.

codeforcescompetitive-programming
CF 104857B - Queue Sorting

We are given a multiset of integers where values range from 1 to n, and each value i appears ai times. The task is to count how many distinct sequences b, which are permutations of this multiset, have a special property involving two queues.

codeforcescompetitive-programming
CF 104857C - Cyclic Substrings

We are given a circular string of digits. From this circle, every pair of indices defines a substring that can wrap around the end back to the beginning.

codeforcescompetitive-programming
CF 104857A - SQRT Problem

We are given three integers: a modulus $n$, and two residues $a$ and $b$, all positive, with $n$ odd and $gcd(a,n)=1$. The task is to recover a unique integer $x$ in the range $1 le x le n-1$ that satisfies two constraints at the same time.

codeforcescompetitive-programming
CF 104869M - Outro: True Love Waits

We are placed in an implicit graph whose vertices are all non-negative integers. Two vertices are connected if their binary representations differ in exactly one bit, and the edge is labeled by the position of that bit (counting from the least significant bit as position 1).

codeforcescompetitive-programming
CF 104869L - Rook Detection

We are working on an interactive system over an $n times n$ grid that contains an unknown set of rooks. The key constraint is not the usual chess interaction, but a visibility condition: every square is initially “controlled”, meaning it is either occupied by a rook or lies…

codeforcescompetitive-programming
CF 104869K - Maximum Rating

We are given an array of integers representing rating changes from several contest rounds. We are allowed to reorder these rounds arbitrarily. We then simulate starting from rating zero, adding values one by one.

codeforcescompetitive-programming
CF 104869J - Graft and Transplant

We are given an unrooted tree with up to 50 vertices. Two players alternate turns, and in each turn they pick an edge $u-v$. The move is not a local swap of endpoints, but a structural “rewiring”: every neighbor of $u$ except $v$ gets detached from $u$ and reattached to $v$.

codeforcescompetitive-programming
CF 104869H - Line Graph Sequence

We are given an undirected simple graph and asked to repeatedly apply the line graph operation. Each application transforms the current graph into a new graph where every vertex represents an edge of the previous graph, and two vertices become adjacent if the original edges…

codeforcescompetitive-programming
CF 104869I - Three Rectangles

We are given a fixed axis-aligned rectangular board with dimensions $H times W$. Onto this board we must place exactly three smaller axis-aligned rectangles, each having fixed dimensions, without rotation.

codeforcescompetitive-programming
CF 104869G - Military Maneuver

We are given a rectangle on the plane. A point is chosen uniformly at random inside this rectangle. That point is the center of a beacon.

codeforcescompetitive-programming
CF 104869F - Ursa Minor

We are given a circular system of positions that represent continents with heights, all starting at zero. The only way to modify these heights is by repeatedly applying operations that choose a fixed segment length and then add an arbitrary real value to every position in some…

codeforcescompetitive-programming
CF 104869E - Sheep Eat Wolves

We are given a river-crossing scenario with two types of animals, sheep and wolves, and a boat controlled by a farmer. Initially, all sheep and wolves are on the left bank.

codeforcescompetitive-programming
CF 104869D - Dark LaTeX vs. Light LaTeX

We are given two strings, one representing a sequence from the “Dark LaTeX” system and one from “Light LaTeX”. From each string we are allowed to pick a contiguous substring. That gives us a pair of substrings, one from the first string and one from the second.

codeforcescompetitive-programming
CF 104869A - Intro: Dawn of a New Era

We are given several “scenes”. Each scene is described by a set of integers representing colors. For every scene, one special value is defined: its main color, which is simply the maximum value inside its set. We must arrange all scenes in a permutation.

codeforcescompetitive-programming
CF 104869C - Swiss Stage

We are tracking a team in a Swiss-system tournament where progress is determined purely by the difference between wins and losses.

codeforcescompetitive-programming
CF 104869B - Turning Permutation

We are working with permutations of the numbers from 1 to n, but only those permutations that satisfy a structural constraint defined through the positions of values rather than the values themselves. For each value i, let qi denote where i appears in the permutation.

codeforcescompetitive-programming
CF 104871A - Attendance

I can’t write a correct Codeforces editorial from that prompt because the actual problem statement is missing. Right now I only see: - Title: “Attendance” - A broken page excerpt (“Page 14 of 26”) - No definition of input, output, or task That’s not enough to…

codeforcescompetitive-programming
CF 104871L - Labelled Paths

We are given a directed acyclic graph where each edge carries a string label. A path’s label is formed by concatenating edge labels in traversal order.

codeforcescompetitive-programming
CF 104871I - Interactive Reconstruction

We are given a hidden tree with $N$ labelled vertices. The structure is unknown, but we are allowed to interrogate it using a special operation. In one query, we send a binary string of length $N$. This string assigns a value of 0 or 1 to each node.

codeforcescompetitive-programming
CF 104871K - Keys

We are given a graph whose vertices are rooms in a mansion and whose edges are doors. Each door connects two rooms and is labeled by a unique key index. To traverse a door, a person must currently hold its key.

codeforcescompetitive-programming
CF 104871J - Jumbled Stacks

We

codeforcescompetitive-programming
CF 104871H - Human Resources

We are given a company hierarchy that forms a rooted tree. Every employee except one has exactly one manager, and each manager has an ordered list of direct reports ranked from most to least preferred.

codeforcescompetitive-programming
CF 104871G - Going to the Moon

We are given two points in the plane, Alice at $A$ and Bob at $B$, and a circle representing the Moon with center $C$ and radius $r$.

codeforcescompetitive-programming
CF 104871F - Phylogenetics

We are given a special graph construction. The base object is a tree, embedded in the plane, with its leaves arranged in circular order. After that, every pair of consecutive leaves in this circular order is additionally connected, forming a cycle on the leaves.

codeforcescompetitive-programming
CF 104871D - Drying Laundry

We are given a fixed collection of laundry items, each item having a physical width and a drying profile. Across multiple weeks, Harry has two parallel clotheslines of equal length, and in each week the available length changes.

codeforcescompetitive-programming
CF 104871E - Equal Schedules

We are given two complete schedules that describe continuous on-call coverage over a timeline that starts at time 0. Each schedule is a partition of the interval into consecutive, non-overlapping segments.

codeforcescompetitive-programming
CF 104871C - Cakes

We are given a bakery that can produce several types of cakes. Each cake recipe consumes some amount of ingredients and requires a set of reusable tools. Every ingredient and every tool has a cost, and each cake also has a selling price.

codeforcescompetitive-programming
CF 104871B - Ball Passing

I can’t write a correct editorial from this as-is because the actual problem statement for “104871B - Ball Passing” is missing.

codeforcescompetitive-programming
CF 104872A - Three Suitcases

We are given three separate suitcases, each contributing a fixed weight to a single combined baggage check-in. The airline does not charge per suitcase, but instead looks at the total weight after everything is combined.

codeforcescompetitive-programming
CF 104872J - Streets of Flatland

We are given a connected structure made of $n$ locations connected by exactly $n-1$ undirected roads, so the underlying graph is a tree.

codeforcescompetitive-programming
CF 104872M - Katya and the Broken Keyboard

Katya wants to type a fixed string, but some keyboard keys behave periodically in a broken way. For each broken letter key, pressing it does not reliably produce a character every time.

codeforcescompetitive-programming
CF 104872L - Count the Christmas Trees

We are asked to count a very structured family of rooted trees of height $n$. The tree is layered: the root is at layer 1, and each vertex at layer $i$ has children only in layer $i+1$.

codeforcescompetitive-programming
CF 104872K - Guess the String

We are given an unknown string of length $n$, made only of the characters a, b, and c. Our task is to reconstruct it by asking queries about adjacent positions. A single query targets a position $i$ and a two-character pattern $u1u2$.

codeforcescompetitive-programming
CF 104872I - Squares

We are working with an infinite integer grid where every operation adds or removes a fixed shape, namely a unit 2 by 2 block anchored at a lower-left coordinate $(x, y)$. Each query toggles the presence of such a block in a current set $S$.

codeforcescompetitive-programming
CF 104872H - Scooter Numbers

We are given a fixed integer $n$. The task is to consider every way of writing $n$ as a sum of positive integers where order does not matter, so each representation is a nondecreasing sequence. Each such representation is treated as a multiset of parts.

codeforcescompetitive-programming