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43815 notes

CF 106237D - Array Transformation

The problem statement is missing from your prompt (the section under Problem Statement is empty), so I don’t have enough information to reconstruct what “Array Transformation” is asking.

codeforcescompetitive-programming
CF 106235D - Three Subsegments

Codeforces 106235D: Three Subsegments

codeforcescompetitive-programming
IMO 2017 Problem 5

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imomathematicsolympiad
CF 106235E - Shortest Non-Shortest Path

We are given a weighted graph where moving along an edge has a cost, and we care about paths from a fixed start node to a fixed target node. Among all possible walks from start to target, there is a minimum possible total cost, the usual shortest path.

codeforcescompetitive-programming
CF 106235F - Almost Bipartite Graph

Got it. Please paste the Codeforces problem statement (or link + full text), and I’ll write a full competitive programming editorial for it.

codeforcescompetitive-programming
CF 106235C - Mafia Cafe

We are simulating a seating system in a cafe where both people and tables are ordered by importance. The key idea is that each person arrives with a fixed time interval during which they occupy a table, and tables cannot host overlapping intervals.

codeforcescompetitive-programming
CF 106235B - Proof of Incorrectness

I don’t actually have the statement of Codeforces 106235B - Proof of Incorrectness available, and I can’t reliably reconstruct it from the title alone without risking inventing details.

codeforcescompetitive-programming
CF 106233L - Хакерская задача

I can’t reliably write a correct editorial for this problem yet because I don’t have the actual statement content for Codeforces 106233L - “Хакерская задача” available here, and I can’t infer it safely from the title alone.

codeforcescompetitive-programming
CF 106233K - Иллюзия размена

The process starts with a single integer placed on a board. You are allowed to repeatedly take any number currently on the board, erase it, and replace it with two positive integers whose sum equals the erased value.

codeforcescompetitive-programming
CF 106233I - Повороты магических меток

We have a sequence of magic marks placed on a plane. The i-th mark has coordinates (xi, yi). A trick chooses a consecutive segment of marks and rotates every mark in that segment around a given point by 90, 180, or 270 degrees clockwise.

codeforcescompetitive-programming
CF 106233J - Теперь ты меня видишь

I can’t reliably write a correct Codeforces editorial from just the problem code/name here because the actual statement is missing.

codeforcescompetitive-programming
CF 106233H - Расширение Всадников

I don’t have the actual problem statement for Codeforces 106233H - “Расширение Всадников”, and without it I can’t produce a correct editorial.

codeforcescompetitive-programming
CF 106233F - Термальные шнуры

The problem is about building a “chain” of substrings taken from a single given string, with a strong nesting constraint. You start with the full string and want to pick several substrings in order from left to right.

codeforcescompetitive-programming
CF 106233E - Иллюзия XOR-а

I can write the full editorial in that format, but I’m missing the actual problem details. The prompt only gives the title “Codeforces 106233E - Иллюзия XOR-а” and empty sections for the statement/input/output.

codeforcescompetitive-programming
CF 106233G - Вечный двигатель

I can’t safely write a correct editorial yet because I don’t have the actual statement of Codeforces 106233G - “Вечный двигатель” (Eternal Engine).

codeforcescompetitive-programming
CF 106233B - Спичечный трюк Лулы

We are given a construction that can be viewed as a very thin lattice made from matches. Imagine two horizontal rows of points, each row containing n positions, and matches connect neighboring points horizontally and vertically, forming a standard 2 by n grid of unit squares.

codeforcescompetitive-programming
CF 106233A - Не иллюзия обмана

I cannot reliably reconstruct Codeforces 106233A “Не иллюзия обмана” from public problemset sources, and I should not guess the statement or solution.

codeforcescompetitive-programming
CF 106233C - Иллюзия суммы

We have a baker with a limited amount of dough and several types of fillings. A bun of a particular filling consumes some amount of dough and some amount of that filling, and gives a certain profit. The baker can also make plain buns that only consume dough.

codeforcescompetitive-programming
CF 106230D - Дело не идёт никуда

The task is about rearranging an array into sorted order, but with a restriction on which swaps are allowed. You are given a sequence of integers, and you are allowed to swap two elements only if at least one of them is a “lucky” number, meaning its decimal representation…

codeforcescompetitive-programming
CF 106230E - Колобки против Энигмы

I can’t reliably reconstruct the full statement of Codeforces 106230E - “Колобки против Энигмы” from available metadata alone, and there isn’t enough accessible problem text in the contest archive to avoid guessing.

codeforcescompetitive-programming
CF 106230A - Гипнотическая мелодия

I can write the full editorial in that format, but I need the actual problem statement or a link to the problem. I could not reliably identify Codeforces 106230A “Гипнотическая мелодия” from the problem ID and title alone, and inventing the algorithm…

codeforcescompetitive-programming
CF 106230B - Ночная операция

I can’t write a correct editorial yet because the actual problem statement for Codeforces 106230B - “Ночная операция” is missing from your message. Right now I don’t know: what the input represents, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
CF 106230C - Рыбий жир без ГМО

I can’t write a correct editorial for this yet because the problem statement is missing. Right now I only have the title “Рыбий жир без ГМО”, but no description of the task, input/output format, or constraints.

codeforcescompetitive-programming
CF 106224B - Fertilizer

We are given a line of fields indexed from left to right. On top of this line, there are several preprogrammed spraying routes. Each route is an interval, meaning it fertilizes every field in some contiguous segment $[Li, Ri]$. A query does not ask about all routes.

codeforcescompetitive-programming
CF 106224A - Monster Battle

I can’t reliably reconstruct Codeforces 106224A - Monster Battle from the title alone, and the editorial needs the exact rules to be correct.

codeforcescompetitive-programming
CF 106224C - Two Trees

Sure. Send me the Codeforces problem statement (or link/text), and I’ll write a detailed competitive programming editorial with: - Problem restatement - Key observations - Intuition behind the solution - Proof of correctness - Algorithm - Complexity analysis - Implementation…

codeforcescompetitive-programming
CF 106223A - Vegetables

We have several vegetables. Vegetable i needs to be produced in quantity Ai, and producing one unit currently consumes Bi units of water. The total water needed is the sum of Ai Bi over all vegetables.

codeforcescompetitive-programming
CF 106223B - Fruits

The setting is a rectangular farm split into an $N times M$ grid. Every cell contains a fruit type represented by an integer, and bees move across the grid using standard four-directional grid steps, always traveling along shortest paths.

codeforcescompetitive-programming
CF 106222B - Secret

I can write the full editorial in that format, but I’m missing the actual problem details for Codeforces 106222B - Secret. The statement fields in the prompt are empty, and I could not reliably identify the problem from the ID alone.

codeforcescompetitive-programming
CF 106222A - River

Each person lives at a position on the north bank and works at a position on the south bank. Walking is only possible along a bank, while crossing the river normally requires a boat that takes B time units.

codeforcescompetitive-programming
IMO 2017 Problem 4

The earlier coordinate idea can be retained only after checking the transformation carefully.

imomathematicsolympiad
CF 106215J - Jaywalking

There are two parallel sidewalks, A and B, each containing positions from 1 through n. You start at position 1 on sidewalk A and want to reach position n on sidewalk B. Moving forward by one position along a sidewalk takes one second.

codeforcescompetitive-programming
CF 106215I - Imaginary Dance Moves

We are given a one-dimensional grid of cells, each cell carrying an integer value that can be positive or negative.

codeforcescompetitive-programming
CF 106215D - Distance Indicators

We are given an array a where each position represents a word and its assigned score. For every pair of indices (i, j) with i < j, the problem defines $$text{dist}(i,j)=ai+aj$$ A pair is considered beautiful when the distance exactly matches the difference between their…

codeforcescompetitive-programming
CF 106215C - Classroom

We are given several test cases. In each test case, there is a circular classroom with $k$ numbered seats arranged in a cycle from $1$ to $k$. Some of these seats are occupied by $n$ students, and each student $i$ is sitting at a known seat position $ai$.

codeforcescompetitive-programming
CF 106215A - An Unfortunate Coincidence

We are given n words. For each word, we must check whether it is exactly the string "WY". If a word is exactly "WY", we replace it with "Whitney Young" in the output. Every other word must be printed unchanged. The input consists of an integer n, followed by n strings.

codeforcescompetitive-programming
CF 106189M - Memory Manager

I cannot reliably reconstruct the full statement of Codeforces 106189M - Memory Manager from the identifier alone, and the problem content is not available in the context you provided.

codeforcescompetitive-programming
CF 106189L - Bitwise operations

including a full proof, implementation details, traced examples, and assert-based tests.

codeforcescompetitive-programming
CF 106189J - Dunno and the cubes

I’m missing a critical piece of information needed to write a correct editorial: the actual statement of Codeforces Gym 106189J is not included in your prompt, and the Gym page is not fully accessible from the available sources.

codeforcescompetitive-programming
CF 106189I - Agronomist

We are given a rectangular garden placed on an infinite integer grid. The rectangle is axis-aligned and described by its lower-left corner and its width and height. So every integer point inside that rectangle, including the boundary, is a potential planting location.

codeforcescompetitive-programming
CF 106189K - Factorials

I can write the editorial, but I don't have the actual statement for Gym/Codeforces 106189K "Factorials". The problem page for Gym 106189K is not publicly accessible through the available sources, and the prompt you provided contains empty sections for the statement, input…

codeforcescompetitive-programming
CF 106189F - Classic Tetris: Scoring

We are given the scoring log of a Tetris player. Each log entry tells us that the player cleared exactly 1, 2, 3, or 4 lines at once, represented by the strings single, double, triple, and tetris. The player starts at level 18.

codeforcescompetitive-programming
CF 106189G - Card deck

I can't reliably write a correct editorial for Codeforces 106189G "Card deck" because the actual problem statement is missing from your prompt, and I could not retrieve the Gym problem text from available sources. Please provide one of the following: 1.

codeforcescompetitive-programming
CF 106189E - Pluses and minuses

We are given a mathematical expression written as a string. It contains non-negative integers, parentheses, and the two binary operators + and -. The structure is already syntactically valid, so every operator sits between two well-formed subexpressions.

codeforcescompetitive-programming
CF 106189D - An oscillating subsequence

We are given an integer sequence and may delete any elements while preserving the order of the remaining ones. The goal is to keep as many elements as possible so that in the resulting subsequence every internal element is a strict peak or a strict valley.

codeforcescompetitive-programming
CF 106189C - And again the maze

We have a rectangular maze. Empty cells are traversable, cells marked X are blocked. The player starts in the top-left corner and wants to reach the bottom-right corner using four-directional moves. We want to place exactly one additional obstacle into an empty cell.

codeforcescompetitive-programming
CF 106189B - Old Tetris

The game log describes a simplified Tetris scoring session where every action is a line clear event of fixed size: a single row clear, a double, a triple, or a four-line clear.

codeforcescompetitive-programming
CF 106189A - Wallpaper

Igor has n walls. Every wall is exactly 3 meters high, and the i-th wall has width ai. The store sells wallpaper rolls that are also 3 meters high, so height never causes any waste. Each roll covers exactly k meters of width.

codeforcescompetitive-programming
CF 106180E - Прятки на дереве

I can't write a correct editorial for Codeforces 106180E from the information provided because the actual problem statement, input format, and output format are missing.

codeforcescompetitive-programming
CF 106180C - Иван и дома

We are given a set of intersections connected by directed roads. Each road can be traversed in its intended direction without cost, but if we go against the direction of a road, we must pay a penalty specific to that road.

codeforcescompetitive-programming
CF 106180D - Обмены рекордов

We are given a sequence that behaves like a list of “records” over time, where each element can be thought of as a score or a value attached to a position. Along with this, we are given a set of allowed exchange operations.

codeforcescompetitive-programming
CF 106180A - Игра с шариками

We are missing the actual statement for Codeforces 106180A - “Игра с шариками”. Without the formal rules, input format, and constraints, any editorial would be a guess, and for Codeforces problems even small mismatches in rules completely change the solution.

codeforcescompetitive-programming
CF 106114G - Gray Transform (Weakened)

We start with an array of size $2^n$ where each position initially stores its own index, so position $i$ holds value $i$. The index $i$ is also interpreted as an $n$-bit binary number. The only non-query operations repeatedly apply a transformation based on Gray code blocks.

codeforcescompetitive-programming
CF 106114C - Arc Path

I don’t have the actual statement for Codeforces 106114C - Arc Path in the prompt, and without it I’d be forced to guess the structure of the problem.

codeforcescompetitive-programming
CF 106114K - Divisor Transformation

I can’t write a correct Codeforces-style editorial for this yet because the actual problem content is missing. Right now I only have the title “Divisor Transformation”, but no definition of what a transformation is, what the input/output mean, or what constraints apply.

codeforcescompetitive-programming
CF 106110D - TL, ML or OK?

We are given a very simplified cost model of a program that runs a loop many times. Each loop iteration does two kinds of work: a number of computational operations and a number of integer insertions into a data structure.

codeforcescompetitive-programming
CF 106110H - Parallel Checking

I cannot responsibly write a correct editorial yet because the problem “Codeforces 106110H - Parallel Checking” is not identifiable from the available statement content.

codeforcescompetitive-programming
CF 106110F - Compromise

I can’t write a correct editorial for this yet because the actual problem statement for “Codeforces 106110F - Compromise” isn’t included, and I don’t have enough reliable context to reconstruct it without risking inventing details.

codeforcescompetitive-programming
CF 106110E - Final Rankings

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 106110E - Final Rankings” could refer to several different tasks depending on the contest context, and without the description (what the input represents, what…

codeforcescompetitive-programming
CF 106110C - Integer Overflow

The task revolves around simulating arithmetic on integers where values can grow beyond the range of standard fixed-width types. You are given a sequence of operations that progressively modifies a single accumulator.

codeforcescompetitive-programming
CF 106110A - Load Distribution

We are given a collection of independent tasks, each with a processing cost, and three identical machines that can execute these tasks. Each task must be assigned to exactly one machine, and a machine’s load is defined as the sum of processing times of tasks assigned to it.

codeforcescompetitive-programming
CF 106110B - What to solve next?

I’m missing the actual statement of Codeforces 106110B (“What to solve next?”). Without the problem description, any editorial would be guesswork, and for Codeforces writeups that quickly leads to incorrect assumptions about the task, constraints, and intended solution.

codeforcescompetitive-programming
CF 106038I - Moscow

The problem statement is missing, so there’s no way to correctly reconstruct what Codeforces 106038I - Moscow is asking. Right now I only see the input/output placeholders without any description of the task, constraints, or operations.

codeforcescompetitive-programming
TAOCP 7.1.1 Exercise 32

Let $c_1,\dots,c_m$ be subcubes of the $n$-cube.

taocpmathematicsalgorithmsvolume-4math-hard
CF 105950O - The Martian

The statement for Codeforces 105950O - The Martian (Problema F: Frodo & Sam) is not actually included in the input you provided. Only the header and empty I/O section are present, so there is no definition of the task, constraints, or required computation.

codeforcescompetitive-programming
CF 105950M - Movieguessr

I’m missing the actual problem statement for 105950M - Movieguessr. The input/output section is empty, so there’s no way to reconstruct what the task is (logic, constraints, or even what is being computed).

codeforcescompetitive-programming
CF 105950N - Ni

Sure - please send me the full problem statement (or a link / screenshot text), and I’ll write a complete Codeforces-style editorial. If you want, you can also tell me: - difficulty rating (if known) - whether you want multiple solutions (e.g.

codeforcescompetitive-programming
CF 105950K - Kill Bill Vol. 1

I can absolutely write that kind of editorial, but I’m missing the only thing that makes it possible: the actual problem statement. Right now you’ve only provided the title and metadata, and “Problema K: Kill Bill Vol.

codeforcescompetitive-programming
CF 105950L - Las Tortuguitas

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

codeforcescompetitive-programming
CF 105950J - John Wick

I don’t have the actual problem statement for Codeforces 105950J - John Wick in your message. Right now only the title is present, so there’s no way to reliably reconstruct the task, constraints, or required output.

codeforcescompetitive-programming
CF 105950H - Cinematic Hierarchy

I can’t reliably write a correct editorial here because the actual problem statement content is missing. Right now I only see the title “Cinematic Hierarchy” with empty input/output sections, so there’s no way to know the task, constraints, or required algorithm.

codeforcescompetitive-programming
CF 105950E - Enigma

We are given two integers that describe a hidden pair of numbers. Think of two unknown values $A$ and $B$. We are not given them directly, but instead we are told their sum and the absolute difference between them.

codeforcescompetitive-programming
CF 105950I - Lost Language

I don’t have the actual statement of Codeforces 105950I - Lost Language in your prompt. What you’ve provided only includes the title and an empty input/output section, so there is no information about what the problem is asking, what operations are allowed, or what…

codeforcescompetitive-programming
IMO 2017 Problem 3

- identify each justification gap,

imomathematicsolympiad
CF 105950D - Inside the Matrix

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now “Codeforces 105950D - Inside the Matrix” is only referenced by name, but there’s no description of the grid/matrix rules, operations, input format, or what needs to…

codeforcescompetitive-programming
CF 105950B - Magic Library

We are given a single lowercase string and allowed to perform at most one operation: choose two positions and swap the characters at those positions.

codeforcescompetitive-programming
CF 105950C - Clichés

We are given a sequence of items where each item belongs to some category, represented by integers. The same value can appear multiple times, and each occurrence is distinguishable only by its position in the input.

codeforcescompetitive-programming
CF 105950A - Absolute Cinema

I can’t write a correct editorial for “Codeforces 105950A - Absolute Cinema” because the actual problem statement is missing. Right now I only see the title and empty Input/Output sections, which isn’t enough to reconstruct what the task is.

codeforcescompetitive-programming
CF 105904J - Joining Polynomials

Sure - please paste the Codeforces problem (statement + constraints, or a link + key details), and I’ll write a full competitive programming editorial for it.

codeforcescompetitive-programming
CF 105904M - Machine for picking shells

We are given a line of shells, each at a fixed position from 1 to N, and each shell has a type represented by an integer.

codeforcescompetitive-programming
CF 105904L - Leaving books at their correct piles

I don’t have the actual statement of Codeforces 105904L - Leaving books at their correct piles, so I can’t reliably derive the logic, constraints, or even what operations are allowed.

codeforcescompetitive-programming
CF 105904H - Hacker in the system

The system starts as an infinite array where position i initially contains the value i. You can think of it as a perfect identity mapping stretched infinitely to the right. This array is grouped into consecutive blocks of fixed length K.

codeforcescompetitive-programming
TAOCP 7.1.1 Exercise 31

We rebuild the solution carefully, fixing all three issues identified in the review.

taocpmathematicsalgorithmsvolume-4hard
CF 105904I - If SSP-SP was longer

The problem statement for Codeforces 105904I - If SSP-SP was longer is missing from your message, so I don’t have the actual rules, input format, or what needs to be computed.

codeforcescompetitive-programming
CF 105904F - Fleeing from the Heat

The problem gives a tree of rooms connected by corridors, where each corridor has a traversal cost. Some rooms contain people who start “occupying” the space at time zero.

codeforcescompetitive-programming
CF 105904E - Enhancing 25 de Março deliveries

I can’t reliably write a correct editorial for this problem yet because the statement is missing. “Codeforces 105904E - Enhancing 25 de Março deliveries” isn’t included in your prompt, and I don’t have access to the actual problem details (inputs, constraints…

codeforcescompetitive-programming
CF 105904G - Guaranteeing SP

I cannot reliably locate the actual statement for Codeforces 105904G - Guaranteeing SP from the available reference data, which strongly suggests it is either a Gym problem or an unpublished/archived problem not indexed in standard mirrors.

codeforcescompetitive-programming
CF 105904D - Dealing with São Paulo Hot Dogs

The issue here is that I cannot reliably reconstruct the exact statement of “Codeforces 105904D - Dealing with São Paulo Hot Dogs” from the available problem index.

codeforcescompetitive-programming
CF 105904A - Amount of food for tigers

The brute-force idea is straightforward: try all seven possible starting days, then simulate day by day, decrementing the corresponding stock until some stock becomes negative. For each start, record how many days we survived, and take the maximum.

codeforcescompetitive-programming
CF 105904C - Cities in Sao Paulo

We are given a collection of cities in São Paulo, where each city is represented as a point on a line or in a structured space depending on the interpretation of the problem input.

codeforcescompetitive-programming
CF 105904B - Bicycle in Ibirapuera

We are missing the actual statement text for “Codeforces 105904B - Bicycle in Ibirapuera” in your prompt, and without it I cannot reconstruct a correct algorithm or produce a valid editorial.

codeforcescompetitive-programming
CF 105837C - Busy Beaver's Colorful Walk

The editorial cannot be written correctly yet because the actual problem content is missing. Right now, only the title “Busy Beaver's Colorful Walk” is provided, but there is no description of the input, output, or rules of the problem.

codeforcescompetitive-programming
TAOCP 7.1.1 Exercise 30

The previous solution failed at one essential point: it treated “$C \subseteq V \cap (V \oplus 2^j)$” as if it could be checked in $O(1)$ time per coordinate without explaining how to avoid enumeratin...

taocpmathematicsalgorithmsvolume-4hard
CF 105833K - Kanto To Johto

The problem can be viewed as a graph exploration problem where each edge is a train line with an associated cost, but the cost is not paid immediately.

codeforcescompetitive-programming
IMO 2017 Problem 2

The equation couples three expressions: $f(xy)$, $f(x+y)$, and $f(f(x)f(y))$.

imomathematicsolympiad
CF 105833I - Independent Inversions

We are given a sequence of positions, each position carrying two values. You can think of it as each index having two “ranks” assigned to it, one from the first ordering and one from the second ordering.

codeforcescompetitive-programming
CF 105833G - Game of Two Choices

We are given a directed graph where each vertex has outgoing edges to a set of neighbors. A token starts at a chosen vertex, and two players move it along edges turn by turn while accumulating a score.

codeforcescompetitive-programming
CF 105833E - Energy Extraction

We are given a collection of energy containers, each starting with some amount of energy. We are allowed to move energy between containers, but every transfer is inefficient: if we move some amount from one container to another, a fixed percentage of what we try to move is…

codeforcescompetitive-programming
CF 105833C - Chimchar Defense

We are given a line of positions from left to right, and each position contains both an enemy and a defender. Enemy at position $i$ starts with a health value $Hi$.

codeforcescompetitive-programming
CF 105822A - Nice Perfect Squares

The problem statement is effectively missing here (it only shows “A”), so there isn’t enough information to derive a correct solution or write a meaningful editorial.

codeforcescompetitive-programming