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tamnd's digital brain — notes, problems, research
41230 notes
We construct a mixed-radix decrementing analogue of Algorithm M, operating in the same state space 0 \le a_j < m_j \quad (1 \le j \le n), but traversing it in reverse lexicographic order by repeatedly...
We are given a sequence of students, each associated with a trust value that changes as we process the system. At any moment, some students are considered to have positive trust, and we are interested in two things: how many students currently have positive trust, and the sum…
We are given a rectangular grid of integers with n rows and m columns. Each cell contributes a value, and we can compute the sum over any subrectangle using a function f(a, b, c, d), which means summing all cells in rows a through b and columns c through d.
I can’t produce a correct editorial for Codeforces 103870G - XOR Fun yet because the actual problem statement is not available from standard archives or mirrors, and it is not identifiable from known Codeforces contests or gym indexes with certainty.
The flaw in the previous solution is not in the identification of trailing maximal components, but in how step M4 is counted inside a single transition.
We are given a line of positions of some length, together with several constraints, each constraint describing a contiguous segment. The task is to decide whether it is possible to assign two types of symbols across the whole line so that all constraints are satisfied.
We are given a sequence that represents spending events over time, where each event is associated with a person identifier. The same person may appear multiple times, forming contiguous segments of activity.
We are working with a simplified calendar of a non-leap year, where the year has 365 days and each day can either contain an event or be empty. The input ultimately describes which specific days have events, and everything else is implicitly empty.
The task is unusually minimal: there is no meaningful structured input to process, and the output is expected to be produced directly based on the problem’s statement rather than any computation over data.
We are tracking a simple repeating process over time. Each day contributes to a running counter that measures how many days have passed since the last reset event.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
Algorithm M visits n-tuples $(a_1,\dots,a_n)$ in lexicographic order induced by the nested loops in (3), so the tuple index corresponds to a mixed-radix expansion with radices $m_1,\dots,m_n$.
I can’t write a correct editorial yet because the problem statement for Codeforces 103886Q - Cereal Trees II isn’t included in your message, and I don’t have enough reliable context to reconstruct it.
I can’t write a correct editorial yet because the actual problem statement for Codeforces 103886O - Vista (Cereal Mountains II) is missing from your message.
We are given a collection of intervals, where each interval represents a “shopping group candidate” occupying a range on a line. Two intervals are considered connected if their ranges overlap at least at one point.
We are given an $n times n$ grid and a number $k$. We need to place $k$ identical objects (called $w$ in the statement) onto distinct cells of the grid. The objective is to maximize a score that depends on how these chosen cells interact with their neighbors in the grid.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
Introduce shifted variables $b_j = a_j - l_j$.
We are working on a grid where only a small number of cells actually matter: a base location and several fossil locations. The grid itself can be large and mostly empty, but movement is only relevant through shortest paths on the grid.
Let $f = \text{COLOR}(x_1,\dots,x_n)$ be the Boolean function encoding proper 4-colorings of the US map, where each vertex variable $x_i$ takes values in ${0,1,2,3}$, represented in binary as in (73).
We are given a sequence of boxes arranged in a line, where each position may contain a box with some property that affects whether it can be shifted left through the line.
We are given a one-dimensional landscape represented by an array of heights. As a water level rises from low to high, positions become submerged once the water level strictly exceeds their height.
We are given a rectangular grid with multiple rows and columns. Each cell in this grid either contains a balloon or a bomb. Two agents move through the grid row by row, and in each row they choose positions in that row to collect balloons.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
The problem statement you provided is incomplete. It only contains the construction idea and does not include the actual input/output specification or sample tests. Because of that, I cannot produce a correct editorial or Python solution.
We are given an array of integers and a requirement to split it into exactly k contiguous subarrays. For any such partition, each subarray has an OR value computed across its elements.
The problem asks us to compute a value for each given integer $x$, where each $x$ represents a “project size” or target sum.
We are working on a geometric optimization problem on a discrete grid. Imagine a 2D classroom-like layout where some cells contain “hall monitors” and the outer boundary of the grid acts like a hard wall that also restricts movement.
We are given a sequence of red pandas sitting in a line, where each panda has an integer ID. The process we care about repeatedly looks at these IDs in increasing order of value, and whenever a particular ID appears in the current line, all pandas with that ID contribute to…
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
Let $G(x,y)$ be the Boolean function defined in (70), representing adjacency in an undirected graph on vertices ${1,\dots,n}$, where $G(x,y)=1$ iff there is an edge between $x$ and $y$.
I can’t write a correct editorial for that problem yet because the actual problem statement is missing. Right now I only see the title “Tyrannosaurus Typing”, but no description of the rules, input format, or what needs to be computed.
I can’t reliably write a correct editorial for this problem yet because the actual problem statement is missing from your prompt. Right now I don’t know what “Carrot Thief” is asking about, what the input represents, or what the required output is.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now we only have the title “Penguin Problems”, but none of the essential information: what the input represents, what operation or computation is required, or what…
The problem statement for “Codeforces 103895F - Rats Rats” is missing from your prompt, so I can’t reliably derive the solution or write a correct editorial without inventing details. Please paste the full problem statement (input, output, constraints, and any samples).
I don’t have the actual statement of Codeforces 103895E - Feed Worm, so I can’t reconstruct the mechanics of the problem reliably.
The problem statement for Codeforces 103895D - Owl Defense is missing from your prompt, so I can’t correctly reconstruct the solution or write a valid editorial.
The problem statement for Codeforces 103895C - Ellie the Elephant isn’t included in your message, so I don’t have the actual rules, input format, or required computation to base an editorial on.
I can’t write a correct editorial for Codeforces 103895A - Love Your Llama without the actual problem statement.
I don’t have the actual problem statement for Codeforces 103896K - Fish Exercise in your prompt (the section is empty), so I can’t reliably reconstruct the task or produce a correct editorial.
I can’t write a correct editorial for Codeforces 103896L - Dog and Friends because the problem statement is missing from your prompt.
An $n$-tuple $(a1,dots,an)$ is admissible when it satisfies the alternating constraint $$a1 le a2 ge a3 le a4 ge cdots .$$ Let $mathcal{A}n$ denote the set of all such binary $n$-tuples.
The problem statement for “Codeforces 103896I - Tyrannosaurus Typing” is missing from your prompt, so there isn’t enough information to derive an algorithm, write an editorial, or construct solutions and test cases.
I can’t write a correct Codeforces editorial for “103896J - Dragon Buffs” without the actual problem statement. Right now the prompt only contains formatting instructions and no description of the task (no input/output definition, constraints, or rules).
I can’t write a correct, detailed editorial without the actual problem statement. “Codeforces 103896H - Penguin Problems” isn’t enough on its own, and I don’t have the input/output description, constraints, or even the core task to reconstruct the solution reliably.
I can’t write a correct editorial for this problem yet because the actual problem statement is missing. “Codeforces 103896G - Carrot Thief” isn’t enough on its own to reconstruct the rules, constraints, or required output, and guessing would very likely produce a…
I don’t have the actual problem statement for Codeforces 103896F - Rats Rats, so I can’t reliably write a correct editorial yet.
We are given a line of cows, each with a weight. A “raid” is defined by two integers, a starting position and a step size. Starting from position a, we repeatedly jump forward by b positions and collect all cows we land on, stopping once we go past the end of the line.
I can’t write a correct editorial for CF 103896C - Ellie the Elephant without the actual problem statement. Right now the prompt contains only the title and metadata, but no description of the task, inputs, or outputs.
We are given a collection of lines in the plane. Each line acts like a reflection axis, and we are interested in sets of points that remain consistent under reflection across every one of these lines.
We are given not one graph but a sequence of graphs that evolve from each other. The first graph is explicitly constructed, and every subsequent graph is obtained from an earlier one by a single edge insertion or deletion.
We are given an undirected tree, and the task is to place each vertex at an integer grid point so that when edges are drawn as straight line segments, the drawing behaves like a clean planar tree embedding with no crossings or unintended intersections.
Equation (65) computes existential quantification over a Boolean variable by combining cofactors of a function $f$ with respect to that variable, typically using the structure of a BDD node whose low...
We are given a strictly convex polygon with vertices listed in counterclockwise order. From this polygon, we look at a growing sequence of prefixes: the polygon formed by the first 3 vertices, then the first 4, and so on until all n vertices.
We are not asked to compute anything for the input. The input is only a seed that the checker uses to generate test expressions. Our task is to output a fixed 1024-word program, i.e.
We are working with two evolving permutations over a set of positions from 1 to n. Initially, both permutations are identical to the identity permutation. One permutation, call it a, can be modified by swapping values at two positions.
We are given two sequences of integers, but neither sequence is provided directly. Instead, both are produced by repeatedly applying the same quadratic recurrence modulo a fixed value.
We are given two players, Alice and Bob, each starting with exactly two known cards from a standard 52-card deck. In addition, six community cards will be chosen from the remaining deck.
We are given a complete poker situation involving ten known cards. Alice starts with two private cards, Bob starts with two private cards, and there are six shared community cards on the table. The players do not draw from an unknown deck, everything is already revealed.
We are dealing with a very rigidly structured Sudoku-like construction, but the actual task is not to solve a Sudoku.
We are given a grid-based puzzle that behaves like a modified Sokoban system with two special entities: a player and a box. Both start on distinct floor cells, and each has a designated target cell.
We are building a sequence of operations that simulate a system with hidden “secret types” from 1 to n. At any moment there is a set of secrets currently present in a zone. However, the crucial complication is that we do not actually know which secret each add refers to.
I don't have enough information to write a correct editorial. The prompt only provides the problem identifier, Codeforces 103920F - Bit Paths, but the Problem Statement, Input, and Output sections are empty.
The problem statement for Codeforces 103920G - Magnetic Backpack is not included in your prompt, so I can’t reliably reconstruct the intended solution or editorial without risking inventing details.
The problem statement for “103920H - Rocks & Fossils Kit - 200+ Piece Set” is missing from your prompt, so I don’t have the actual task definition, input/output format, or constraints needed to write a correct Codeforces-style editorial.
I can’t write a correct editorial for Codeforces 103920E - “It’s Raining Rocks!” because the actual problem statement is missing from your prompt.
The problem statement is missing from the prompt, so I can’t reliably reconstruct what “Coats of Paint” (Codeforces 103920D) is asking.
I don't have enough information to write a correct editorial. The prompt identifies the problem as Codeforces 103920C - Earthbending years, but the actual problem statement, input format, output format, and constraints are all missing: Without those details, I cannot determine…
I don’t have the actual statement of Codeforces 103920A - Truck Driver, so I can’t responsibly write a correct editorial for it yet.
The statement section is empty, so there isn’t enough information to reconstruct the problem for “Anya’s Rocks” or write a correct editorial.
Equation (65) computes existential quantification over a Boolean variable by combining cofactors of a function $f$ with respect to that variable, typically using the structure of a BDD node whose low...
I’m missing the actual problem statement for Codeforces 103921J - Rock Balancing, so I can’t safely reconstruct the solution or write a correct editorial yet.
I can’t write a correct editorial yet because the actual problem statement for “103921I - Cabinet Search” is missing from your prompt.
I can't write a correct editorial because the prompt does not include the actual problem statement. For Codeforces 103921H - Rocks & Fossils Kit - 200+ Piece Set, the sections labeled Problem Statement, Input, and Output are empty.
The problem statement for CF 103921G - Magnetic Backpack is missing from your prompt, so I can’t reliably reconstruct the intended model, constraints, or solution strategy.
I can’t reliably write a correct editorial for Codeforces 103921F - Bit Paths without the actual problem statement.
I can’t reliably write a correct editorial for “Codeforces 103921D - Coats of Paint” because the problem statement is missing from your prompt, and I don’t have enough information to reconstruct the task from the title alone.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “103921E - It’s Raining Rocks!”, but no description of the grid, rules, operations, or required output.
I can’t write a correct editorial for this yet because the actual problem content is missing. “Codeforces 103921C - Earthbending years” is referenced, but there’s no statement, no input/output description, and no constraints.
We are given two positive integers written in plain decimal form, each without leading zeros, and we need to compare them using a deliberately odd rule inspired by the story.
We are given several complete rankings of the same set of universities. Each ranking is a permutation, ordered from best to worst.
We are given an undirected simple graph, meaning there are no self-loops and no duplicate edges. From this starting graph, we are allowed to add new edges between previously non-adjacent pairs of vertices, while keeping the graph simple.
We are working in a 2D plane where movement is normally continuous and costs time proportional to Euclidean distance. The plane contains rectangular forbidden zones that cannot be entered, although their borders are allowed.
We are given a long lowercase string s. We process it from left to right, and after reading each prefix s[1..i], we must compute a score that depends on a dictionary of special words. Each dictionary word ti has an associated value vi.
A Morse code word of length $n$ is a sequence over the alphabet ${cdot, -}$ in which each dot contributes weight $1$ and each dash contributes weight $2$, and the total weight is exactly $n$.
We are simulating a random process that builds a graph on $n$ labeled vertices. The graph starts empty. In each iteration, we independently pick two vertices $u$ and $v$ uniformly from $1$ to $n$, allowing $u=v$.
We are given a single weapon model described by two parameters and a replay of a match segment. The weapon deals at most $B$ damage per bullet and has a firing rate of $R$ rounds per minute. From this we can deduce how frequently bullets can be fired.
A Morse code word of length $n$ is a sequence over the alphabet ${cdot, -}$ in which each dot contributes weight $1$ and each dash contributes weight $2$, and the total weight is exactly $n$.
We are given a source string $S$ and a target string $F$. The task is to cut out a contiguous segment of $S$, meaning a substring, such that $F$ can still be found inside that segment as a subsequence.
We are given a deterministic sequence generator that starts from a value $a$ and repeatedly applies a quadratic transformation $x mapsto x^2 + b$. Each query defines one such infinite sequence.
Equation (65) computes existential quantification over a Boolean variable by combining cofactors of a function $f$ with respect to that variable, typically using the structure of a BDD node whose low...
We are given a hidden string of length $n$, where every character is either an opening bracket or a closing bracket. We do not see the string directly, but we are given a set of interval constraints.
We are given a fixed equation format of length 8, always written as two two-digit numbers added together and equated to another two-digit number. The structure is always ??+??=??, where each ? is a digit.
We are modeling a process that runs for discrete seconds, where each second produces a reward equal to the current stamina value. The stamina starts at some initial value $S$, and naturally decreases by 1 each second as time passes.
We are given a graph of post offices connected by bidirectional routes. A message starts at some office, travels along a simple path to another office, and at every intermediate office the message’s “mark” is flipped.
We are given a sequence of n days. On each day i there are two exchange rates: one for dollars and one for Brazilian reals, both measured in Egyptian pounds.
We are given a straight railway line where every point can be treated as an integer coordinate on a number line. Each resident has a home position and a work position on this line, and they start walking toward work at time zero with speed 1 unit per second.
We are given an undirected weighted graph representing cities connected by roads. Initially, the graph is connected. Each road has a strength value. A road is considered “critical” if removing it disconnects the graph. In graph terms, this is exactly a bridge.