brain
tamnd's digital brain — notes, problems, research
41641 notes
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.
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.
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 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.
We are building a number of grams of food that Thiago will offer. Each valid offering must be composed of baskets of fixed size A, so the total amount must be a multiple of A.
We are given two sets of entities: historians and paintings. Each historian can be assigned to at most one painting, and each painting can be assigned to at most one historian, so any valid solution is a matching in a bipartite graph.
We are given a collection of words, each paired with a positive value. A valid “spell” is a sequence of words where every next word must extend the previous one by exactly one or more characters, meaning the previous word is a proper prefix of the next.
We are given several independent strings, each representing a name made of lowercase English letters. The transformation rule defines how a new version of the string is constructed: every character is inspected together with its immediate neighbors, and the character is…
We start with a row of spheres labeled from 1 to N in increasing order. Two agents repeatedly shrink this row by removing every second remaining element, but they sweep in opposite directions.
We are given a collection of $n$ distinct primes $a1, a2, dots, an$. From these primes we form a single huge product $P = prod ai$. Each item in the store is defined in an unusual way: the price of item $i$ is the product of all primes except $ai$.
We are maintaining a sequence of numbers arranged in a line, where each position represents a fig tree and the value at that position is the number of figs on that tree.
There are three independent taxi services, each running an infinite sequence of shared tuk-tuks between a city center and a hotel. Each service has its own travel time and capacity.
We are given a collection of time intervals, each representing the construction period of a building. A chosen day corresponds to sending the army to inspect all buildings that are under construction on that day.
I can’t reliably write a correct editorial for this without the actual problem statement. “Codeforces 103937I - Moldy Sandwich” isn’t something I can reconstruct from metadata alone, and guessing would almost certainly produce a wrong solution, wrong algorithm, and…
A monotone Boolean function $f(x1,dots,x5)$ is uniquely represented by its set of minimal true points, an antichain $A subseteq 2^{[5]}$, and conversely every antichain determines such a function by upward closure.
Let $f$ be a Boolean function represented by an ordered reduced BDD, and let $x_j$ be the variable being eliminated.
The problem statement for Codeforces 103937H - Competing Clubs is not included in your message (the “Problem Statement / Input / Output” sections are empty).
The problem statement is missing, so I can’t accurately reconstruct or explain the solution for “Codeforces 103937G - Larry Longsleeves”.
I can’t produce a correct editorial for this problem as-is because the actual problem statement (the definitions of “diverse debaters”, input format, and required output) is missing.
I can’t write a correct editorial yet because the actual problem statement for Codeforces 103937F - Bat-shoe Toss is not included in your message.
I don’t have the actual statement of Codeforces 103937D “Hardcore Haircuts” in your prompt, so I can’t reliably reconstruct the problem or produce a correct editorial.
At the moment, there is no description of what the input represents, what operations are allowed, or what must be computed as output.
I don’t have the actual statement of Codeforces 103937A - Jeopardy! in your prompt, and without it I can’t reliably reconstruct the intended task, constraints, or solution path.
Algorithm C in this section evaluates a BDD bottom-up by assigning to each node $v$ a value depending only on its LO and HI successors, with sink nodes providing the base cases and each internal node combining results from its children.
I can’t produce a correct editorial yet because the actual problem statement for Codeforces 103938I - Moldy Sandwich isn’t included in your message.
The problem statement for Codeforces 103938J - Quantum Chaos is missing from your prompt, so I don’t have any information about what the task actually asks (input format, required output, or the underlying model).
Algorithm C in this section evaluates a BDD bottom-up by assigning to each node $v$ a value depending only on its LO and HI successors, with sink nodes providing the base cases and each internal node combining results from its children.
I can’t produce a correct editorial yet because the problem statement is missing. Right now the only information provided is the title “Competing Clubs”, but there is no description of the rules, input format, or required output.
I can’t safely write a correct editorial yet because the full problem statement for “103938G - Larry Longsleeves” is not reliably available from your prompt, and the title alone is not enough to reconstruct the exact task without risking inventing details.
The problem statement is not included in your prompt, so I don’t have the actual rules, input format, or required computation for Codeforces 103938F - Bat-shoe Toss.
I can’t reliably write a correct editorial for this problem yet because the statement for “Codeforces 103938D - Hardcore Haircuts” is missing from your prompt.
I’m missing the actual problem statement for Codeforces 103938C - Robot Inspection, so I can’t reliably reconstruct the task or derive a correct algorithm without guessing.
Let a multiset ${a_1,\dots,a_n}$ be given, and assume Algorithm L of Section 7.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title “Limited Increasing Sequences”, but there is no definition of: what the input represents, what constraints apply, or what needs to be computed.
Let $f(x1,dots,xn)$ be a Boolean function with truth table $tau$ and BDD $T(f)$. Recall from Section 7.1.4 that a function is sweet when every subtable corresponding to a prefix assignment is a bead, equivalently every node in its ordered decision structure corresponds to a…
The problem statement is missing (the Input/Output and actual description are empty), so there’s no way to reconstruct the task reliably from what you provided.
I’m missing the actual problem statement for Codeforces 103940J - Joining the KAK, so I can’t reliably reconstruct the intended model or derive a correct solution yet.
The problem statement section is empty, so I don’t have enough information to reconstruct what “How Many Laughs” is asking or what the input/output represent.
I can write the full Codeforces-style editorial, but I’m missing the actual problem statement for 103940I - Inversion Counting.
The problem statement is missing from your prompt, so there is no way to reconstruct the task, constraints, or required algorithm reliably.
I’m missing the actual problem statement for Codeforces 103940F - Famous Paintings, so I can’t safely reconstruct the solution or write a correct editorial.
The problem statement is missing from your prompt, so there isn’t enough information to derive the solution, constraints, or even the core task for “Express Warehouse Migration”.
The problem statement is missing from your prompt, so there’s no way to reconstruct the task, constraints, or required output.
I don’t have the actual statement for Codeforces 103940A - Advanced Player Setup, so I can’t reliably reconstruct the problem or produce a correct editorial without guessing.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “Correcting School Enrollment Errors”, but no definition of the input, output, or constraints.
We are given a tree with n nodes, and each node carries a distinct label from 0 to n − 1, so the labels form a permutation.
We are given a multiset of short strings, each up to length 5000 in total across all inputs. From these strings, we care about which longer strings “qualify” certain fragments. A fragment is a partition of a string t into consecutive pieces.
We are given a function on the set of integers from 1 to n. Each number points to exactly one number in the same range, so the function can be seen as a directed graph where every node has exactly one outgoing edge. We are also given many queries.
We are given a three dimensional grid representing a building. Every point in this grid is a room identified by coordinates $(x, y, z)$. Movement inside this building is not done by walking, but by using special cyclic elevators.
We are given several binary strings, all of equal length. Think of them as a matrix with n rows and m columns, where each entry is either 0 or 1. Each row is a string, and each column is a bit position shared across all strings. We then perform a sequence of operations.
The problem gives a grid of size 4 by m. The top row contains exactly one entry point at column x, and water starts flowing downward from that cell. The bottom row contains exactly one exit point at column y, and it can only accept water flowing downward into it.
We are working with finite sets of non-negative integers. Given a set $A$, we define the sumset $A + A$ as all values that can be formed by adding any two elements from $A$, with repetition allowed in the choice but duplicates removed in the result.
We are given a single long string made of lowercase English letters. From this string, we are allowed to delete characters and keep the remaining ones in order, forming a subsequence.
A Boolean function is sweet when every subtable arising from any prefix assignment is a bead. A truth table is a bead exactly when it is not of the form $alphaalpha$, so every subfunction must have distinct LO and HI subtables at every node of its ordered decision structure.
We are given a convex polygon that rotates rigidly around a fixed point, which is guaranteed to lie inside the polygon or on its boundary. Along with this, we are given two parallel lines that form an infinite strip.
We are given a string over the alphabet A, B, C, D that changes over time. Two operations are supported: we can cyclically increment every character in a range, and we can ask how many different “exam papers” could produce a given substring while using exactly k questions.
We are given a circular string made only of four characters, each mapped to a small integer weight. The string is arranged in a ring, so after the last character we wrap back to the first.
A truth table of order $n$ is a binary string of length $2^n$. A bead is a truth table $beta$ that is not of the form $alphaalpha$. A Boolean function is sweet if every subtable obtained by fixing any prefix of variables is a bead.
We are given a grid of size $R times C$ where each cell contains either a known integer or a missing value represented by a question mark.
We are given the coordinates of all vertices of a convex polyhedron in three-dimensional space. We are allowed to rotate this solid arbitrarily in 3D, then “shine a light” from a fixed direction and look at the orthogonal projection of the polyhedron onto a plane.
A truth table of order $n$ is a binary string of length $2^n$. A bead is a truth table $beta$ that is not of the form $alphaalpha$. A Boolean function is sweet if every subtable obtained by fixing any prefix of variables is a bead.
Each test case gives a collection of identical vertical blocks, where every block is a cuboid with one fixed dimension equal to 1 and two other dimensions $ai$ and $bi$.
We are simulating a constrained random assignment process for 32 football teams. The teams are already divided into four fixed tiers, each tier containing exactly eight teams.
We are given 14 distinct playing cards. From these, we must discard exactly one card and then split the remaining 13 cards into three poker hands: a 3-card front hand, a 5-card middle hand, and a 5-card back hand.
Let $x = (x_1,\dots,x_n)_2$ and let the successor sequence in exercise 91 be $x,\, x\oplus 1,\, x\oplus 2,\, \dots,$ where $x\oplus k$ is binary addition mod $2^n$.
We are building a periodic tiling of an $R times C$ rectangle, and then repeating it infinitely in both directions. So the entire plane is determined by a finite matrix of size $R times C$, where each cell is assigned one of $K$ colors.