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tamnd's digital brain — notes, problems, research
41641 notes
We are given an array of integers and asked to extract as many disjoint contiguous segments as possible such that each chosen segment has XOR equal to zero.
We are given a number and allowed to repeatedly modify it using a very specific operation. In one move, we pick any positive integer whose decimal form is made only of the digit 3, such as 3, 33, 333, and so on, and add it to the current value.
I can’t reliably write a correct editorial for this yet because the actual problem content for “Codeforces 106290D - 小丑牌” is missing from your message (the statement section is empty).
I can’t write a correct editorial yet because the actual problem statement for “Codeforces 106272I - Euler” is missing from your prompt.
We are given a line of farmland split into $n$ consecutive plots. Each plot initially contains some amount of wheat.
I don’t have the actual statement of Codeforces 106267B - 排列之差 available in your prompt (the “Input/Output” section is empty), so I can’t reconstruct a correct algorithm or editorial without risking hallucinating the problem.
We are given two very large square matrices $A$ and $B$, but they are not provided in full. Instead, each matrix is described only by its nonzero entries. Every missing position is implicitly zero, and the number of nonzero entries is small compared to $n^2$.
We are given a target image on an $n times m$ grid. Each cell contains either a color label or zero, where zero means transparent.
We are given an array of integers, and we want to determine whether there exists a special value $X$ such that the array can be split into two groups with a very strong number-theoretic relationship to $X$.
We are working with an unknown array of positive integers indexed from 1 to N. A key structural promise is that any two different elements of this array are coprime, so their greatest common divisor is always 1.
We are given an array of integers where both the array values and the modulus values are bounded by 50,000. Each query does not ask for a single computation, but for a nested sum: we pick a segment of the array and then, for every modulus value in a given range, we compute the…
We are given a collection of affine transformations of a single integer variable, all starting from zero. Each operation takes the current value of $x$ and replaces it with $ai x + bi$, where both coefficients are non-negative integers.
The problem statement for “Codeforces 106238I - Heart Lingers, Future Fades” is effectively empty in the input you provided. There is no description of the input format, output format, constraints, or even the computational task itself beyond the title line.
We are given a range of possible outcomes for a hidden integer value $p$, which represents Godflex’s final ranking. We only know that $p$ lies somewhere in an interval $[l, r]$, and nothing more. Alongside this uncertainty, there are several bookmaker offers.
We start with a segment of integers $[l, r]$. At any moment, the process maintains two things: the current segment and a running score initialized to zero. Each round consists of two random choices.
We are given a very small and unusual restriction on the exponent in a power equation of the form $a^n + b^n = c^n$. Unlike classical number theory settings where $n$ is large, here $n$ is guaranteed to be either 0 or 1.
We are given a line of merchants, each holding a single item with a price. The price of the i-th merchant is an integer in the range from 0 to $2^k - 1$, and every price is conceptually stored as a fixed-length k-bit binary number. The system processes three types of operations.
We are given an $n times m$ grid, and we are allowed to choose a single starting cell on the boundary of this grid. From that chosen cell, a process starts that spreads to all four neighboring cells each second, exactly like a breadth-first expansion on a grid.
We are given a sequence of non-negative integers, and we are allowed to optionally apply a digit-reversal operation to any element. Each number can be reversed independently, but only once. After performing these choices, we obtain a final array, and we want to maximize its mex.
We are simulating a process of placing small fixed shapes into a large grid, where the grid behaves like a physical system: cells get filled, whole rows disappear when completely filled, and everything above a removed row collapses downward.
We are given a closed interval of integers from L to R, and we must arrange all these integers into a permutation so that the ordering between any pair of numbers depends entirely on whether they are coprime.
We are simulating a very small programming language that modifies a single integer register $A$, starting from zero. Each instruction either adds a value to $A$ or overwrites $A$ completely with a value.
The building can be thought of as a fixed catalog of rooms distributed across floors, where each floor has a known set of possible room slots and each slot corresponds to one or two actual living places.
We are given a sequence of test cases. Each test case contains a single integer $n$, and for each one we conceptually build an $n times n$ multiplication table where the cell in row $a$ and column $b$ contains the product $a cdot b$.
I can’t reliably write a correct editorial from what you’ve provided because the actual problem statement is missing. Right now I only see the title “Codeforces 106184B - 天才琪露诺与雾之湖的宝藏”, but the input/output and rules are blank.
We are given a square roof with integer coordinates, from $(0,0)$ to $(S,S)$, and a set of hatch positions inside it. We must choose a single point on the roof where a leash is attached.
We are given several short strings made of lowercase letters, and for each string we want to find another string in the same set that is “closest” under a specific distance measure.
We are given two strings of equal length. One is the observed encrypted text, and the other is a candidate original message that we believe might have been encrypted to produce it. The encryption process is two-layered.
We are given a sequence of song “hype” values in a fixed order, and we are allowed to delete some songs while keeping the remaining ones in their original relative order. From the remaining subsequence, we want a very structured pattern.
We are given a complete graph on n cities, where every pair of cities has a direct road. The cost of that direct road is not uniform: it depends on the bitwise AND of the two city values.
We are given a collection of items. Each item has a weight and a value, but for some items exactly one of these two numbers is missing and must be assigned by us as a positive integer not exceeding one billion. Two greedy procedures will later run on the completed dataset.
We are given a sequence of songs, each associated with a value that can be positive or negative. We want to select a subset of these songs to maximize the total sum of selected values, but there is a spacing restriction: if we choose a song at position i, then we are forbidden…
We have $n$ wizards arranged in a circle, indexed from 1 to $n$. Each wizard starts with a very large identical mana value, so initially all wizards are tied. Then we apply $q$ rituals. Each ritual defines a sequence of affected wizards.
The task revolves around deciding whether a given fraction produces a terminating decimal or an infinite repeating decimal when written in base 10. Each test case gives an integer denominator, and we implicitly consider the fraction $frac{1}{n}$.
We are given an array of distinct performance scores recorded over time. Each query provides a small set of time indices, and from those indices we consider every possible interval formed by choosing two of them as endpoints, including choosing the same index twice only when…
We are given a string of brackets. Two players alternately remove characters from the ends of this string. On each move, a player picks either the leftmost or rightmost character of the current string and deletes it.
We are given an array of integers, and for every position we must answer a separate optimization question about that position’s value. The element at index i is treated as a fixed reference element.
We are given an array and for every prefix of this array we must compute a value formed from all unordered pairs inside that prefix.
We are working on an infinite grid where a white king starts at a given coordinate and must eventually capture all black rooks. The king moves like a standard chess king, meaning it can step to any of the eight neighboring cells in one move.
We start with the identity permutation, meaning the array contains numbers from 1 to n in increasing order. We are allowed to repeatedly apply a recursive construction that behaves like a binary splitting process.
The task reduces to constructing a single string based on an input integer. We are given a number $n$, and we must output a line consisting of exactly $n$ identical characters, where each character is the percent symbol %.
We are asked to construct a single permutation of the numbers from 1 to n, interpreted as building heights along a row. Two integers a and b describe how many buildings are visible when looking from the left end and from the right end respectively.
We start with a collection of chopsticks grouped by type. Each type contributes a known number of identical items. From the full pool, we randomly select exactly 2n chopsticks without replacement.
We are given a string for each test case and we want to measure how far it is from being a palindrome, where “distance” is the standard edit distance with insertions, deletions, and substitutions allowed.
We are given a simple closed fence described by its corner points in clockwise order. The fence forms a convex polygon, so every interior angle is less than 180 degrees and every line segment between two interior points stays inside the region.
I can’t write a correct editorial for this problem yet because the actual problem statement is missing. Right now I only see the title “Share Auction” with no rules about bids, constraints, input format, or what needs to be optimized.
I’m missing the actual problem statement for Codeforces 106082B - Simplified Calendar System. Right now the input/output sections are empty in your prompt, so there’s no way to correctly reconstruct: - what the calendar system defines (days, months, weeks, etc.
We are given a one-dimensional wall made of consecutive segments, each segment having an initial height. We are allowed to perform exactly one reinforcement operation.
Each student in this problem can be represented by a bitmask of length $K$, where the $j$-th bit indicates whether the student has a particular frontend skill.
We are given a polynomial where every coefficient is either 0 or 1, so the polynomial is best thought of as a set of powers of x. If the coefficient of $x^k$ is 1, we include that term, otherwise we do not.
We are given a tree where every vertex initially carries a distinct label equal to its index. The only allowed action is a single global operation that changes some of these labels. In that operation, we first pick a simple path in the tree.
We are given a pool of programming problems, each problem already labeled by exactly which of three students can solve it. Every problem falls into one of seven categories depending on its solvability set among students 1, 2, and 3.
We are given a fixed amount of time, measured in hours, during which electricity is available. Each hour corresponds to exactly one washing cycle of a machine. There are several colors of clothes, and each color has a certain number of items that must all be washed.
We are given a string, and we are asked multiple independent queries on it. Each query focuses on a contiguous substring. For that substring, we are allowed to modify characters, where one operation means replacing a single character with any other lowercase English letter.
We are given an array, and we repeatedly apply a randomized operation on it. One step of the process picks an index uniformly at random and overwrites that position with the median of the remaining elements.
We are given an array of positive integers. For each $k$, we look at all ways to choose exactly $k$ elements and record the sum of each such choice. This produces a multiset $Sk$, where repetition matters because different subsets can produce the same sum.
We are given a binary string $s$. We are allowed to cut it into a sequence of contiguous pieces, and the cut points are completely flexible, meaning every split of the form “choose $k$ and break into $k$ substrings” is valid, and all such splits are counted.
We are given two integers, $k$ and $m$. Think of building a target sum $n$ by splitting it into exactly $k$ ordered parts, where each part is a non-negative integer. Two decompositions are different if any position in the $k$-tuple differs.
We are given an integer array and we want to examine every contiguous segment of it. For each segment, we compute the greatest common divisor of all elements inside that segment.
We are given a multiset of divisors of an unknown integer $X$, but one divisor is missing. In total, $X$ has exactly $N+1$ positive divisors, and we are given $N$ of them.
We are given a permutation of length $N$, meaning it contains each number from 1 to $N$ exactly once. From this permutation, we define a transformation called “taking a semi-fixed point”: an index $x$ is counted if applying the permutation twice brings us back to $x$…
We are given a binary string where some positions are already fixed as 0 or 1, while others are unknown and marked with ?. We must replace every ? with either 0 or 1. After filling the string, we look at adjacent pairs and count how many times consecutive characters differ.
We are given a target array $b$ of length $n$. Our task is not to compute a value from a permutation, but to reconstruct a permutation $a$ of numbers from $1$ to $n$ such that a derived function computed from $a$ matches $b$.
We are given an undirected graph where each edge carries a 60-bit weight. A path between two vertices is evaluated not by summing or minimizing weights, but by taking the bitwise AND of all edge weights along that path.
We are given a convex polygon with vertices listed in counterclockwise order. From this polygon, we must choose three vertices, call them $a$, $b$, and $c$, also in counterclockwise order along the boundary.
We are working inside an axis-aligned rectangle whose lower-left corner is fixed at the origin and whose upper-right corner is at $(n, m)$. Inside this rectangle there are $k$ forbidden lattice points.
We are given a tree with vertices labeled from 1 to n, and these labels also define a linear order. For any interval [l, r], we look at the vertices whose labels lie in this range and consider the subgraph induced by them in the original tree.
We are given a sequence of N strings, each string representing a “scroll” written with lowercase letters. From each scroll, we care about all substrings that are palindromes, and we treat two substrings as the same if their character sequences are identical, regardless of…
We are given a sequence of length $2N$, where each value from $1$ to $N$ appears exactly twice. You can think of it as pairs of identical symbols placed along a line. The task is to choose pairs of equal symbols under a strict movement rule.
We are given a fixed number of nights, D, and a collection of N possible places where a person can sleep. Each place i comes with a constraint di that limits how many consecutive nights can be spent in that place.
We are given a very small grid, at most 8 by 8, where each cell can be in one of three states. A cell can be alive, dead, or blocked. Blocked cells never change and also never participate as active contributors in the dynamics. The system evolves in discrete steps.
We are given a set of ingredients and a list of ingredients that Antonio refuses to use. The recipe is split into several stages, and each stage specifies a subset of ingredients required for that step. When Antonio prepares a stage, he simply omits every ingredient he dislikes.
We are given a simple polygon representing a room, with the first vertex acting as a door. Inside this polygon lies a single point representing a towel. A person starts at the door vertex, walks entirely within the polygon, reaches the towel, and must return to the same door.
We are given two starting years, one for Master Wei and one for Kai. From those years onward, each person accumulates “experience” equal to the number of years that have passed since they started programming.
We are given a sequence consisting only of two types of symbols, an opening bracket ( representing a Yang dancer and a closing bracket ) representing a Yin dancer. Each ( must be matched with a later ) to form a valid pairing, and every dancer participates in exactly one pair.
We are given a sequence of distinct integers and a specific version of quicksort that behaves in a very particular way. The pivot is always chosen as the middle index of the current segment, not by value but by position.
We are given a sequence of integers, and we are allowed to choose a modulus value $M$ with $1 < M le 10^9$. Once $M$ is fixed, each “move” consists of picking a remainder value $x$, and in that move we remove all numbers whose value modulo $M$ equals $x$.
We are given a chronologically sorted list of distinct integers, where each integer represents a day on which Bernardo went to the gym. The goal is to determine the longest streak of consecutive calendar days present inside this list.
We are given a short string of up to 15 characters representing coins in a line. Each coin is either H (heads) or T (tails).
The problem statement you provided is incomplete. It only contains the label “K”, with no description of the input format, constraints, or required output.
The task is deceptively minimal: there is no meaningful structure to process, and the entire problem reduces to producing a specific string consisting of alternating characters.
We are trying to reconstruct an unknown binary string of length $N$ by interacting with a judge. Each time we submit a candidate string, the judge compares it against the hidden password and returns how long the two strings match from the beginning.
We are given a set of distinct fish names, all equally likely to be chosen. Jake wants to identify the chosen fish by asking yes or no questions, and he is allowed to ask any question he wants, as long as the answer partitions the remaining candidates into two groups.
We are given a circular arrangement of parentheses. The string contains only '(' and ')', and the total number of opening and closing brackets is equal. We are allowed to take a prefix of the string and move it to the end, effectively rotating the string.
The problem statement is missing from the prompt (the input/output sections are empty), so there’s no way to reliably reconstruct what Codeforces 106033C “Conveyors” is asking.
I can’t write a correct editorial for this yet because the actual problem statement is missing (it only shows “I”).
I can’t write a correct Codeforces editorial from that input because the actual problem content is missing. Right now, the statement is just: with empty input/output sections.
There are several independent groups of items, each group representing a competition. For each competition $i$, Fmota initially owns $ai$ shirts. Time is measured in years starting from year 0 up to year $k$.
There are $n$ tuk-tuks arranged in a strict ranking where position 1 is the best and position $n$ is the worst. Each tuk-tuk has a hidden score, and the ordering is always strictly determined by these scores: higher score means better position, and all scores are distinct at…
We are given a sequence of integers representing transactions that are accumulated one by one into a running sum. The machine computing this sum has a fixed integer range determined by a parameter $k$, so the running total must always stay inside a symmetric interval around zero.
The prompt is missing the actual problem statement, input format, and output requirements. Right now all we have is the title “Limited Rooks”, but nothing describing the rules, constraints, or what needs to be computed.
The problem statement for Codeforces 106033J - Journey is missing from your prompt (it only shows “J” with no description, input, or output details). Without the actual statement, it’s not possible to write a correct or meaningful editorial.
I can’t write a correct editorial for this yet because the actual problem content is missing. Right now the statement is effectively just “H”, with no description of the graph structure, operations, input format, or required output.
The problem statement for “Codeforces 106033E” is not actually included here beyond a placeholder (“E”). Without the actual description, constraints, or input/output format, it’s impossible to derive a correct solution or write a meaningful editorial.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the title “106033D - Disregard the Light”, but there is no description of the rules, input format, or what needs to be computed.
This request cannot be completed faithfully as written because the problem statement is missing. The only content provided under Problem Statement is: with no description of rules, input format, output format, constraints, or samples.
The input describes a sequence of independent test cases, where each test case consists of a small structured configuration that must be validated under a fixed procedure defined by the problem.
We are given a collection of items, where each item has two values attached to it. One value represents a benefit, interpreted as “how much you learn”, and the other represents a cost or pain, interpreted as “how much it hurts”.
We are given a ranking of $n$ teams, ordered from best position $1$ to worst position $n$. Each position has an associated “happiness” value, but instead of being arbitrary, the sequence follows a very specific shape: it first never increases as we go from position $1$…
We are tracking a vote among four fixed candidates, the turtles Rafael, Leonardo, Donatello, and Michelangelo. Each candidate already has some number of votes, and there is a pool of remaining votes that have not yet been cast.