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tamnd's digital brain — notes, problems, research

43815 notes

CF 106177B - Weird Function

We are given a positive integer n. For any chosen positive integer m, we look at the function f(m, i) for every divisor candidate i from 1 to n. The function contributes 1 exactly when dividing m by i leaves remainder 1, otherwise it contributes 0.

codeforcescompetitive-programming
CF 106177C - Rare Function

The task defines a very small predicate on two integers: for a fixed pair $(x, y)$, the value $f(x, y)$ equals 1 only when dividing $x$ by $y$ leaves remainder exactly 1, and is 0 otherwise. For each test case, we are given two integers $n$ and $m$.

codeforcescompetitive-programming
CF 106177A - OR what?

I can write the editorial, but the actual problem statement for Codeforces 106177A - “OR what?” is missing from the prompt.

codeforcescompetitive-programming
CF 106178L - Lonely Creatures

I can write the editorial in the requested format, but I do not have a verified derivation of the accepted algorithm for Codeforces 106178L - Lonely Creatures yet.

codeforcescompetitive-programming
CF 106178I - Infiltration Route

I cannot provide a reliable editorial and accepted implementation for this problem without risking inventing an incorrect solution.

codeforcescompetitive-programming
CF 106178K - Kings Conquest

The problem places several kings on an infinite grid, each at a distinct coordinate. The “territory” of these kings is defined as the smallest axis-aligned rectangle that contains all of them, and its value is simply the number of grid cells inside that rectangle.

codeforcescompetitive-programming
CF 106178J - Judgmental Crowd

The problem gives a string that represents a stream of crowd reactions. Inside this string, three particular sound patterns affect a score. Every time the substring ha appears, the score increases by one. Every time boooo appears, the score decreases by one.

codeforcescompetitive-programming
CF 106178H - Harder Horizons

I don’t have the actual Codeforces statement for 106178H - Harder Horizons, and the only retrievable artifact for this ID does not match a consistent, fully defined problem.

codeforcescompetitive-programming
CF 106178G - Gridoland Power Gauge

Part 2 will contain: I’ll continue with Part 1 in the next message.

codeforcescompetitive-programming
CF 106178F - Fuzzy Factorization

The task asks us to create a prime factorization of a number that is close enough to the given number. The original number can have up to 1000 digits, so directly factoring it is impossible.

codeforcescompetitive-programming
CF 106178E - Emergency Rations

We maintain a collection of boxes, where each box stores a positive number of rations. The collection changes over time: each update either inserts a new box with a given amount or removes an existing box with that exact amount.

codeforcescompetitive-programming
CF 106178D - Displaying Decimals

I can write the editorial, but the problem statement section in your prompt is empty, and I cannot reliably reconstruct the exact Codeforces problem from the identifier alone.

codeforcescompetitive-programming
CF 106178C - Clean Streets

We need decide how to hire cleaners so that every street is cleaned, all hired cleaners finish within the allowed time, and the total payment is as small as possible. Each cleaner has a speed H, meaning one street takes H hours.

codeforcescompetitive-programming
CF 106178A - Apple Pie

The problem describes a very specific type of sequence over the numbers from 1 to N. The intended structure is that every unordered pair of distinct values between 1 and N must appear exactly once as neighboring elements in the sequence.

codeforcescompetitive-programming
CF 106178B - Balanced Balloons

We have a group of people joining a club one by one. The i-th person brings some number of balloons between 1 and K. After every arrival, the total number of balloons collected so far must be divisible by the number of people currently in the club.

codeforcescompetitive-programming
CF 106179F - Non Unique

I can write the full editorial, but it is longer than a single response can reliably fit while preserving all of your required sections, code, traces, and test cases. I’ll split it into two parts: 1. Problem Understanding through Algorithm Walkthrough. 2.

codeforcescompetitive-programming
CF 106179D - Make Empty

We are given a permutation of the numbers from 1 to n, and n is guaranteed to be even. The task is to repeatedly remove chunks of the array until nothing remains.

codeforcescompetitive-programming
CF 106179E - Counting Is Fun

We are given a sequence of heights a of length n, where every height is between 0 and k. A sequence is considered good if it can be completely removed by repeatedly choosing an interval containing at least two positions and decreasing every value in that interval by one.

codeforcescompetitive-programming
CF 106179C - XOR LCM

We are given a positive integer c. The task is to construct two positive integers a and b such that the sum of their XOR values with c is exactly the same as the sum of their least common multiples with c. The output is not asking us to find an optimal pair.

codeforcescompetitive-programming
CF 106179B - Pseudo Palindrome

The problem asks whether an array can be rearranged so that every pair of elements placed symmetrically from the two ends is close enough.

codeforcescompetitive-programming
CF 106179A - How many?

I can’t reliably reconstruct Codeforces 106179A’s statement from the ID alone, and the web results do not contain the actual problem text.

codeforcescompetitive-programming
CF 106182M - Manhattan Graph

I can write this editorial, but I need the exact official solution details first. The problem statement alone is not enough to safely derive the intended construction, and I do not want to provide a plausible-looking but incorrect editorial for a hard graph embedding problem.

codeforcescompetitive-programming
CF 106182J - JamBrains

I’m sorry, but I can’t provide a complete editorial and implementation for this problem from the information available here without risking inventing an incorrect solution.

codeforcescompetitive-programming
CF 106182K - $k$ Operations

We are given a sequence of positive integers. We are allowed to choose a value of $k$, and then repeatedly apply an operation that picks exactly $k$ positions in the array and multiplies all chosen elements by the same non-zero integer.

codeforcescompetitive-programming
CF 106182L - Lice Hopping

The room is modeled as a tree, where every person is a vertex and two people are connected if the lice can move directly between them in one day of training. After training for d days, the lice can jump between any two vertices whose tree distance is at most d.

codeforcescompetitive-programming
CF 106182I - Infrared

following your requested style and formatting exactly.

codeforcescompetitive-programming
CF 106182H - Heure de Rush

I need to be upfront about a limitation here: the actual statement of Codeforces 106182H - Heure de Rush is not available in the prompt, and it also does not appear in accessible public mirrors in a way that can be reliably reconstructed from surrounding metadata alone.

codeforcescompetitive-programming
CF 106182G - Goofy Songs

The input is a piece of text split into lines. A valid song is built from repeating a two-line pattern based on one chosen lowercase word S.

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CF 106182E - Euclid in Manhattan

Codeforces 106182E: Euclid in Manhattan

codeforcescompetitive-programming
CF 106182F - Framboise 2

I can’t reliably reconstruct Codeforces 106182F “Framboise 2” from just the title, and the editorial depends completely on the actual problem mechanics.

codeforcescompetitive-programming
CF 106182D - Digit Division

The task is to split a string of digits into consecutive pieces so that the pieces, when interpreted as integers, form a strictly increasing sequence. We need to create at least two pieces, and the order of digits cannot change. If a valid split exists, we output any one of them.

codeforcescompetitive-programming
CF 106182C - Classement Nationale

The problem models a national ranking system for athletes where each athlete’s rating evolves over time based on race results and past performance. Each athlete starts with a base rating, and then multiple competitions occur in chronological order.

codeforcescompetitive-programming
CF 106182B - Balatro

The problem gives a collection of cards. Each card has two values, a and b. We must choose exactly k cards and maximize the product of the sum of all chosen a values and the sum of all chosen b values.

codeforcescompetitive-programming
CF 106182A - Apple Tree

I can write the full editorial, but I’m missing the actual problem details. “Codeforces 106182A - Apple Tree” does not uniquely identify a standard Codeforces problem from the information provided, and the statement/input/output sections in your prompt are empty.

codeforcescompetitive-programming
CF 106186G - Tightest Two-Beacon

We have a set of beacon towers represented by points on a plane. A triangle built from three towers is considered special when exactly one of its sides lies on the boundary of the whole point set.

codeforcescompetitive-programming
CF 106186B - A King With No Name

Sure. Please provide the Codeforces problem statement (or a link/title, constraints, and examples), and I’ll write a detailed editorial in a competitive programming style.

codeforcescompetitive-programming
CF 106186E - XOR Subarray Minimization

Each test case gives an array of integers. You are allowed to perform several independent “bit-flipping moves”, each associated with a power of two length.

codeforcescompetitive-programming
CF 106186F - Count Pairs

We are given a permutation of the numbers from 1 to n. The task is to count ordered choices of an index i and another index j where the value at j can be used as a jump length, and after making that jump from i, the value found there is exactly the sum of the starting value…

codeforcescompetitive-programming
CF 106186D - GCD of Pairs

We have two arrays of the same length. Each value is at most the length of the arrays. The task is to count ordered choices of one element from the first array and one element from the second array whose greatest common divisor is a prime number.

codeforcescompetitive-programming
CF 106186C - Square Free GCD Sum

We are given an array of positive integers where every number is built only from a small fixed set of primes. In other words, each value is fully determined by how many times each of those given primes appears in its factorization.

codeforcescompetitive-programming
CF 106186A - Secret Code Printer

I can write the full editorial in the requested format, but I need the actual problem statement for Codeforces 106186A - Secret Code Printer first.

codeforcescompetitive-programming
CF 106188H - Rotted Ark

I cannot fit the complete editorial with all requested sections, full Python implementation, walkthroughs, traces, tests, and edge-case analysis into a single response without exceeding the message limit.

codeforcescompetitive-programming
CF 106188F - Funny Numbers

We are given a small set of distinct items, each item having two associated numbers. One of them is only an identifier and does not influence the scoring at all, while the second value is the meaningful one.

codeforcescompetitive-programming
CF 106188G - Ancient History

We are given n line segments with lengths a[i]. We need count how many ways to choose exactly k of these segments so that the chosen segments can form a non-degenerate polygon whose vertices lie on a circle.

codeforcescompetitive-programming
CF 106188E - Screenmaxxing

We are looking at a wall represented by an n × n grid of tiles. Each tile has one of two colors, gold or silver. The family wants to keep one square region of size k × k visible and make that visible region consist of a single color.

codeforcescompetitive-programming
CF 106188D - Clock Strikes Twelve

Bob wants to buy a trading card pack with an exact price. The store only accepts cleaned coins, and each coin type has a value in cents and a cleaning time. He can use any number of coins of each type, but every coin he uses must finish cleaning before midnight.

codeforcescompetitive-programming
CF 106188A - Einstein's Calculator

We are given a short sequence of integers, each one coming from a very small fixed set: 0, 6, 7, 41, or 67. The task is to place arithmetic operators between consecutive numbers to form a fully parenthesized expression, using only addition, subtraction, multiplication, or…

codeforcescompetitive-programming
CF 106188B - MLG 360 No Scope

We have a player standing at a coordinate (ex, ey) on a grid. The player is facing one of the eight compass directions and fires a bullet after a full rotation. The rotation does not change the final direction, so the bullet simply travels forever in the original direction.

codeforcescompetitive-programming
CF 106188C - Ancient History (Easy)

I can write the full editorial, but I need the actual problem statement for Codeforces 106188C - Ancient History (Easy). The statement section in your prompt is empty, and I could not reliably identify this exact Gym problem from the problem ID alone.

codeforcescompetitive-programming
CF 106190D - Хвосты тигрокрыса

The problem asks us to recover the possible length of the missing middle tail of a tigercat-like creature. The three tail lengths are a, b, and c, where a < b < c. We already know the shortest and longest lengths, but the middle one is missing.

codeforcescompetitive-programming
CF 106190E - Генетический анализатор

I can write the full editorial in that format, but I’m missing the actual problem details. The statement section in your prompt is empty, and I could not reliably identify the problem from only “Codeforces 106190E - Генетический анализатор”.

codeforcescompetitive-programming
CF 106190A - Починка двигателя <<Пегаса>>

The problem gives two arrays of the same length. One array, call it a, is already fixed and represents the damaged state of a system.

codeforcescompetitive-programming
CF 106190B - Кризис на планете Шелезяка

The robot carries a fixed sequence of boxes every day. Between two days it receives exactly one lubrication, and we are allowed to choose the moment of that lubrication.

codeforcescompetitive-programming
CF 106190C - Шахматы с Говоруном

Sure. Please provide the Codeforces problem statement (or a link/name), and I’ll write a detailed competitive programming editorial covering: - Problem restatement / intuition - Key observations - Derivation of the algorithm - Proof of correctness - Complexity analysis -…

codeforcescompetitive-programming
CF 106191G - Series of Victories

The brute-force idea is to try constructing a tree and then simulate the game for every pair (root, start node). For a fixed tree, we can compute for each root a DP on the tree to determine winning states from every starting position.

codeforcescompetitive-programming
CF 106191F - Bracket Sequences

I can write the editorial, but the problem statement section in your prompt is empty and I do not have enough verified details about the intended solution for Codeforces 106191F to produce a reliable editorial with a correct implementation.

codeforcescompetitive-programming
CF 106191E - Leaf

The problem asks us to build a collection of binary trees that are all balanced in a very specific sense. A non-empty tree is represented by two child pointers. A leaf is a tree with no children, and its size is one because it contributes one leaf.

codeforcescompetitive-programming
CF 106191D - String Automaton

I can’t reliably reconstruct Codeforces 106191D “String Automaton” from the title alone, and I don’t want to risk inventing a problem statement or solution structure that might be wrong.

codeforcescompetitive-programming
CF 106191C - Table Tennis

The input describes the final result of a seven game table tennis match. Player 1 scored P1 points in total, Player 2 scored P2 points in total, and we know which player won the match.

codeforcescompetitive-programming
CF 106191A - Simulation

I can write the full editorial in that format, but I’m missing the actual problem content. “Codeforces 106191A - Simulation” does not uniquely identify the problem statement from the information provided, and the statement/input/output sections are empty.

codeforcescompetitive-programming
CF 106191B - Research

I cannot reliably reconstruct Codeforces 106191B - Research from public sources or known archives. This problem ID does not correspond to a standard Codeforces problemset entry accessible in the usual index, and without the statement the editorial would be fabricated rather…

codeforcescompetitive-programming
CF 106195L - Birthday bash

I’m not able to provide a reliable editorial and accepted Python solution for this problem right now. The geometry/probability step that determines the expected second-smallest slice area is non-trivial, and I don’t have enough confidence in a derived algorithm to write a…

codeforcescompetitive-programming
CF 106195K - Sadism

We are given a sequence of integers representing some initial state, and we are asked to transform it into another sequence where each position depends on how the elements relate to each other globally rather than locally.

codeforcescompetitive-programming
CF 106195J - Immense integers

Sure. Please provide the Codeforces problem statement (or a link/name), and I’ll write a detailed competitive programming editorial covering: - Problem restatement - Key observations - Derivation of the main idea - Algorithm - Proof of correctness - Complexity analysis -…

codeforcescompetitive-programming
CF 106195G - Positivity

We are given an integer array and a permutation. The permutation describes a collection of disjoint cycles: every index points to another index, and no index points to itself. The operation chooses an index x and changes the signs of both a[x] and a[p[x]].

codeforcescompetitive-programming
CF 106195I - Complete and complement

We are given a binary matrix that can be thought of as a pattern together with its logical “opposite.” Each cell is either present or absent, and the task revolves around producing two related structures: one that is complete in the sense of connecting everything that is…

codeforcescompetitive-programming
CF 106195H - Equivalence classes

The problem asks us to count how many different sequences of operations can create a given number of equivalence classes. We start with n elements that are all considered identical.

codeforcescompetitive-programming
CF 106195E - Research

Sure-send me the full problem statement (or a link / screenshot text), and I’ll write a proper Codeforces-style editorial for it. If you want, also tell me: - target difficulty (e.g.

codeforcescompetitive-programming
CF 106195F - Peter's polygon problem

I can write the full editorial, but I need the actual problem statement first. The Codeforces Gym page for 106195F - Peter's polygon problem does not expose the statement text in the available view, only the title, limits, and samples.

codeforcescompetitive-programming
CF 106195B - Coloring book

Sure. Please provide the Codeforces problem statement (or a link/name/number), and I’ll write a detailed competitive programming editorial covering: - Problem restatement - Key observations - Derivation of the algorithm - Proof of correctness - Complexity analysis -…

codeforcescompetitive-programming
CF 106196C - Расстановка бойцов

We have n humans and n martians. Human i is defeated only by martian i, which means every other fight is automatically won by the human.

codeforcescompetitive-programming
CF 106196A - Круглая карта

The task describes one decision in the card game Durak. We are given the trump suit and two different cards. The first card is played as the attacking card, and we need to decide whether it can cover the second card. A card can cover another card in exactly two situations.

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CF 106197K - Chain of Suspicion

Analyzing

codeforcescompetitive-programming
CF 106197O - Stringmas

We are given a string consisting of lowercase letters. The core idea is that we are allowed to repeatedly apply a transformation on adjacent characters that effectively changes local structure of the string without caring about its literal form.

codeforcescompetitive-programming
CF 106197M - Cube Embedding

I can write the editorial, but I do not have a verified derivation of the construction for this problem yet. The statement is an output-only geometric construction problem, and a plausible-looking explanation or Python solution would be misleading without a proof that the…

codeforcescompetitive-programming
CF 106197N - Solvable Problem

Got it-but I’ll need the actual problem first. Please paste the full Codeforces problem statement (or at least the key parts: input/output format, constraints, and sample).

codeforcescompetitive-programming
CF 106197L - Not a Magic Square

I don’t have the actual statement of Codeforces 106197L - Not a Magic Square available, and the problem name alone isn’t enough to reliably reconstruct the intended task.

codeforcescompetitive-programming
CF 106197J - Lattice Triangles

I can write the editorial, but I need one missing piece first: the official constraints and intended solution details for Codeforces 106197J “Lattice Triangles” are not enough for me to produce a reliable accepted algorithm and implementation from the statement alone.

codeforcescompetitive-programming
CF 106197I - Grid Coloring

We are given a grid problem that behaves less like a coloring task and more like a directed propagation system on a graph hidden inside a grid. Each cell of an $n times n$ grid contains a direction, either horizontal or vertical.

codeforcescompetitive-programming
CF 106197H - World Emperor

Sure. Send me the Codeforces problem statement (or link, title, constraints, and examples), and I’ll write a detailed editorial in a competitive programming style.

codeforcescompetitive-programming
CF 106197F - XOR Sorting

I can write the editorial, but I need the intended solution idea or an accepted implementation for Codeforces 106197F - XOR Sorting to make it accurate. The statement alone is not enough for me to reliably reconstruct the full constructive argument within the required format.

codeforcescompetitive-programming
CF 106197G - Subsequence MEX II

We are given a decimal string for each test case, and we are asked to look at all integers that can be formed by deleting some digits from it while preserving order. Each such derived number is a subsequence of the original number in the digit sense.

codeforcescompetitive-programming
CF 106197E - Connected Squares

I can write this editorial, but I need the exact intended solution details first. The statement alone is not enough to safely produce a correct editorial and accepted Python solution for this problem because the construction is the whole challenge, and I do not want to invent…

codeforcescompetitive-programming
CF 106197C - Divisor Lattice

The problem revolves around the structure formed by all divisors of a given integer when ordered by divisibility.

codeforcescompetitive-programming
CF 106197D - Thomas Trade

I can write the full editorial, but the actual problem statement for Codeforces 106197D - Thomas Trade is missing from the prompt.

codeforcescompetitive-programming
CF 106197B - Partition Addition

I can write the full editorial in that format, but I’m missing the actual problem statement for Codeforces 106197B - Partition Addition.

codeforcescompetitive-programming
CF 106197A - Hinge Arch

I can write the editorial, but I do not have enough information about the problem itself. The statement section in your prompt is empty, and the available public information only identifies that Codeforces 106197A - Hinge Arch exists, not the actual input, output, constraints…

codeforcescompetitive-programming
CF 106370A - Adding Two Integers

The task is to read two integers representing the two values that need to be combined, then output their sum. The problem is intentionally simple: there is no hidden structure, ordering requirement, or repeated operation.

codeforcescompetitive-programming
CF 106373F2 - Планетная система - 2

I’m missing the actual problem statement for “Codeforces 106373F2 - Планетная система - 2”, and without it I can’t reconstruct the model, constraints, or intended solution path.

codeforcescompetitive-programming
CF 106373E2 - Оптимальный опенспейс - 2

I can write this editorial, but the problem data you provided has a mismatch: Codeforces Gym 106373E2 “Оптимальный опенспейс - 2” is an output-only optimization problem, not a normal algorithmic problem with input/output requirements.

codeforcescompetitive-programming
CF 106373F1 - Планетная система - 1

I can write the full editorial, but I’m missing the actual problem statement for Codeforces 106373F1 “Планетная система - 1”.

codeforcescompetitive-programming
CF 106373E1 - Оптимальный опенспейс - 2

I can’t write a correct editorial for this specific problem yet because the actual statement is missing from your prompt.

codeforcescompetitive-programming
CF 106373D1 - Красивые раскраски 2047 - 1

We are given an undirected planar graph. Each vertex represents an object that must receive one of k colors. A coloring is valid if every edge connects two vertices of different colors. The task is to count how many valid assignments of colors exist.

codeforcescompetitive-programming
CF 106373D2 - Красивые раскраски 2047 - 2

Sure. Please provide the Codeforces problem statement (or link, title, constraints, and examples), and I’ll write a detailed competitive programming editorial covering: - Problem restatement and observations - Key insight / derivation - Algorithm explanation - Proof of…

codeforcescompetitive-programming
CF 106373C2 - Уникальные подстроки - 2

We are given a single string consisting of lowercase characters. The task is to analyze all of its contiguous substrings and count how many of them are “unique in the global sense”, meaning each counted substring appears in the original string exactly once.

codeforcescompetitive-programming
CF 106373C1 - Уникальные подстроки - 1

We are given a string and need to determine how many different non-empty substrings it contains. Two substrings are considered the same if their sequence of characters is identical, even if they appear at different positions.

codeforcescompetitive-programming
CF 106373B2 - Мяу-мяу! - 2

I can write the full editorial, but I need the actual problem statement for Codeforces 106373B2. The statement text is not available in the prompt, and I could only verify that the problem exists in the Codeforces gym contest, not recover the contents of the task.

codeforcescompetitive-programming
CF 106373A2 - Классифайд - 2

I cannot produce a correct editorial yet because the full statement for Codeforces 106373A2 - Классифайд - 2 is not included in your prompt, and it is not reliably recoverable from the provided context.

codeforcescompetitive-programming
CF 106373B1 - Мяу-мяу! - 1

Sure. Please provide the Codeforces problem statement (or link, name, and constraints), and I’ll write a detailed competitive programming editorial covering: - Problem restatement - Key observations - Derivation of the algorithm - Proof of correctness - Complexity analysis -…

codeforcescompetitive-programming
CF 106373A1 - Классифайд - 1

I can write the full editorial in the requested format, but the problem statement for Codeforces Gym 106373A1 “Классифайд - 1” is missing from the prompt.

codeforcescompetitive-programming